#!/bin/env python
# -*- coding: utf-8 -*-

"""
This file is part of the web2py Web Framework
Copyrighted by Massimo Di Pierro <mdipierro@cs.depaul.edu>
License: LGPLv3 (http://www.gnu.org/licenses/lgpl.html)

Thanks to
    * Niall Sweeny <niall.sweeny@fonjax.com> for MS SQL support
    * Marcel Leuthi <mluethi@mlsystems.ch> for Oracle support
    * Denes
    * Chris Clark
    * clach05
    * Denes Lengyel
    * and many others who have contributed to current and previous versions

This file contains the DAL support for many relational databases,
including:
- SQLite & SpatiaLite
- MySQL
- Postgres
- Oracle
- MS SQL
- DB2
- Interbase
- Ingres
- SapDB (experimental)
- Cubrid (experimental)
- CouchDB (experimental)
- MongoDB (in progress)
- Google:nosql
- Google:sql
- Teradata
- IMAP (experimental)

Example of usage:

>>> # from dal import DAL, Field

### create DAL connection (and create DB if it doesn't exist)
>>> db = DAL(('mysql://a:b@localhost/x', 'sqlite://storage.sqlite'), folder=None)

### define a table 'person' (create/alter as necessary)
>>> person = db.define_table('person',Field('name','string'))

### insert a record
>>> id = person.insert(name='James')

### retrieve it by id
>>> james = person(id)

### retrieve it by name
>>> james = person(name='James')

### retrieve it by arbitrary query
>>> query = (person.name=='James') & (person.name.startswith('J'))
>>> james = db(query).select(person.ALL)[0]

### update one record
>>> james.update_record(name='Jim')

### update multiple records by query
>>> db(person.name.like('J%')).update(name='James')
1

### delete records by query
>>> db(person.name.lower() == 'jim').delete()
0

### retrieve multiple records (rows)
>>> people = db(person).select(orderby=person.name, groupby=person.name, limitby=(0,100))

### further filter them
>>> james = people.find(lambda row: row.name == 'James').first()
>>> print james.id, james.name
1 James

### check aggregates
>>> counter = person.id.count()
>>> print db(person).select(counter).first()(counter)
1

### delete one record
>>> james.delete_record()
1

### delete (drop) entire database table
>>> person.drop()

Supported field types:
id string text boolean integer double decimal password upload blob time date datetime

Supported DAL URI strings:
'sqlite://test.db'
'spatialite://test.db'
'sqlite:memory'
'spatialite:memory'
'jdbc:sqlite://test.db'
'mysql://root:none@localhost/test'
'postgres://mdipierro:password@localhost/test'
'postgres:psycopg2://mdipierro:password@localhost/test'
'postgres:pg8000://mdipierro:password@localhost/test'
'jdbc:postgres://mdipierro:none@localhost/test'
'mssql://web2py:none@A64X2/web2py_test'
'mssql2://web2py:none@A64X2/web2py_test' # alternate mappings
'oracle://username:password@database'
'firebird://user:password@server:3050/database'
'db2://DSN=dsn;UID=user;PWD=pass'
'firebird://username:password@hostname/database'
'firebird_embedded://username:password@c://path'
'informix://user:password@server:3050/database'
'informixu://user:password@server:3050/database' # unicode informix
'google:datastore' # for google app engine datastore
'google:sql' # for google app engine with sql (mysql compatible)
'teradata://DSN=dsn;UID=user;PWD=pass; DATABASE=database' # experimental
'imap://user:password@server:port' # experimental

For more info:
help(DAL)
help(Field)
"""

###################################################################################
# this file only exposes DAL and Field
###################################################################################

__all__ = ['DAL', 'Field']

MAXCHARLENGTH = 2**15 # not quite but reasonable default max char length
DEFAULTLENGTH = {'string':512,
                 'password':512,
                 'upload':512,
                 'text':2**15,
                 'blob':2**31}
TIMINGSSIZE = 100
SPATIALLIBS = {
    'Windows':'libspatialite',
    'Linux':'libspatialite.so',
    'Darwin':'libspatialite.dylib'
    }

import re
import sys
import locale
import os
import types
import cPickle
import datetime
import threading
import time
import cStringIO
import csv
import cgi
import copy
import socket
import logging
import copy_reg
import base64
import shutil
import marshal
import decimal
import struct
import urllib
import hashlib
import uuid
import glob
import traceback
import platform

CALLABLETYPES = (types.LambdaType, types.FunctionType, types.BuiltinFunctionType,
                 types.MethodType, types.BuiltinMethodType)


###################################################################################
# following checks allow the use of dal without web2py, as a standalone module
###################################################################################
try:
    from utils import web2py_uuid
except ImportError:
    import uuid
    def web2py_uuid(): return str(uuid.uuid4())

try:
    import portalocker
    have_portalocker = True
except ImportError:
    have_portalocker = False

try:
    import serializers
    have_serializers = True
except ImportError:
    have_serializers = False

try:
    import validators
    have_validators = True
except ImportError:
    have_validators = False

logger = logging.getLogger("web2py.dal")
DEFAULT = lambda:0

sql_locker = threading.RLock()
thread = threading.local()

# internal representation of tables with field
#  <table>.<field>, tables and fields may only be [a-zA-Z0-0_]

regex_type = re.compile('^([\w\_\:]+)')
regex_dbname = re.compile('^(\w+)(\:\w+)*')
regex_safe = re.compile('^[\w_]+$')
regex_table_field = re.compile('^([\w_]+)\.([\w_]+)$')
regex_content = re.compile('(?P<table>[\w\-]+)\.(?P<field>[\w\-]+)\.(?P<uuidkey>[\w\-]+)\.(?P<name>\w+)\.\w+$')
regex_cleanup_fn = re.compile('[\'"\s;]+')
string_unpack=re.compile('(?<!\|)\|(?!\|)')
regex_python_keywords = re.compile('^(and|del|from|not|while|as|elif|global|or|with|assert|else|if|pass|yield|break|except|import|print|class|exec|in|raise|continue|finally|is|return|def|for|lambda|try)$')
regex_select_as_parser = re.compile("\s+AS\s+(\S+)")

# list of drivers will be built on the fly
# and lists only what is available
drivers = []

try:
    from new import classobj
    from google.appengine.ext import db as gae
    from google.appengine.api import namespace_manager, rdbms
    from google.appengine.api.datastore_types import Key  ### needed for belongs on ID
    from google.appengine.ext.db.polymodel import PolyModel
    drivers.append('google')
except ImportError:
    pass

if not 'google' in drivers:

    try:
        # first try pysqlite2 else try sqlite3
        try:
            from pysqlite2 import dbapi2 as sqlite3
            drivers.append('pysqlite2')
        except ImportError:
            from sqlite3 import dbapi2 as sqlite3
            drivers.append('SQLite3')
    except ImportError:
        logger.debug('no sqlite3 or pysqlite2.dbapi2 driver')

    try:
        # first try contrib driver, then from site-packages (if installed)
        try:
            import contrib.pymysql as pymysql
        except ImportError:
            import pymysql
        drivers.append('pymysql')
    except ImportError:
        logger.debug('no pymysql driver')

    try:
        import psycopg2
        from psycopg2.extensions import adapt as psycopg2_adapt
        drivers.append('psycopg2')
    except ImportError:
        logger.debug('no psycopg2 driver')

    try:
        # first try contrib driver, then from site-packages (if installed)
        try:
            import contrib.pg8000.dbapi as pg8000
        except ImportError:
            import pg8000.dbapi as pg8000
        drivers.append('pg8000')
    except ImportError:
        logger.debug('no pg8000 driver')

    try:
        import cx_Oracle
        drivers.append('Oracle')
    except ImportError:
        logger.debug('no cx_Oracle driver')

    try:
        import pyodbc
        drivers.append('MSSQL/DB2/Teradata')
    except ImportError:
        logger.debug('no MSSQL/DB2/Teradata driver')

    try:
        import Sybase
        drivers.append('Sybase')
    except ImportError:
        logger.debug('no Sybase driver')

    try:
        import kinterbasdb
        drivers.append('Interbase')
    except ImportError:
        logger.debug('no kinterbasdb driver')

    try:
        import firebirdsql
        drivers.append('Firebird')
    except ImportError:
        logger.debug('no Firebird driver')

    try:
        import informixdb
        drivers.append('Informix')
        logger.warning('Informix support is experimental')
    except ImportError:
        logger.debug('no informixdb driver')

    try:
        import sapdb
        drivers.append('SAPDB')
        logger.warning('SAPDB support is experimental')
    except ImportError:
        logger.debug('no sapdb driver')

    try:
        import cubriddb
        drivers.append('Cubrid')
        logger.warning('Cubrid support is experimental')
    except ImportError:
        logger.debug('no cubriddb driver')

    try:
        from com.ziclix.python.sql import zxJDBC
        import java.sql
        # Try sqlite jdbc driver from http://www.zentus.com/sqlitejdbc/
        from org.sqlite import JDBC # required by java.sql; ensure we have it
        drivers.append('zxJDBC')
        logger.warning('zxJDBC support is experimental')
        is_jdbc = True
    except ImportError:
        logger.debug('no zxJDBC driver')
        is_jdbc = False

    try:
        import ingresdbi
        drivers.append('Ingres')
    except ImportError:
        logger.debug('no Ingres driver')
    # NOTE could try JDBC.......

    try:
        import couchdb
        drivers.append('CouchDB')
    except ImportError:
        logger.debug('no couchdb driver')

    try:
        import pymongo
        drivers.append('mongoDB')
    except:
        logger.debug('no mongoDB driver')

    try:
        import imaplib
        drivers.append('IMAP')
    except:
        logger.debug('could not import imaplib')

PLURALIZE_RULES = [
    (re.compile('child$'), re.compile('child$'), 'children'),
    (re.compile('oot$'), re.compile('oot$'), 'eet'),
    (re.compile('ooth$'), re.compile('ooth$'), 'eeth'),
    (re.compile('l[eo]af$'), re.compile('l([eo])af$'), 'l\\1aves'),
    (re.compile('sis$'), re.compile('sis$'), 'ses'),
    (re.compile('man$'), re.compile('man$'), 'men'),
    (re.compile('ife$'), re.compile('ife$'), 'ives'),
    (re.compile('eau$'), re.compile('eau$'), 'eaux'),
    (re.compile('lf$'), re.compile('lf$'), 'lves'),
    (re.compile('[sxz]$'), re.compile('$'), 'es'),
    (re.compile('[^aeioudgkprt]h$'), re.compile('$'), 'es'),
    (re.compile('(qu|[^aeiou])y$'), re.compile('y$'), 'ies'),
    (re.compile('$'), re.compile('$'), 's'),
    ]

def pluralize(singular, rules=PLURALIZE_RULES):
    for line in rules:
        re_search, re_sub, replace = line
        plural = re_search.search(singular) and re_sub.sub(replace, singular)
        if plural: return plural

def OR(a,b):
    return a|b

def AND(a,b):
    return a&b

def IDENTITY(x): return x

def varquote_aux(name,quotestr='%s'):
    return name if regex_safe.match(name) else quotestr % name

if 'google' in drivers:

    is_jdbc = False

    class GAEDecimalProperty(gae.Property):
        """
        GAE decimal implementation
        """
        data_type = decimal.Decimal

        def __init__(self, precision, scale, **kwargs):
            super(GAEDecimalProperty, self).__init__(self, **kwargs)
            d = '1.'
            for x in range(scale):
                d += '0'
            self.round = decimal.Decimal(d)

        def get_value_for_datastore(self, model_instance):
            value = super(GAEDecimalProperty, self).get_value_for_datastore(model_instance)
            if value is None or value == '':
                return None
            else:
                return str(value)

        def make_value_from_datastore(self, value):
            if value is None or value == '':
                return None
            else:
                return decimal.Decimal(value).quantize(self.round)

        def validate(self, value):
            value = super(GAEDecimalProperty, self).validate(value)
            if value is None or isinstance(value, decimal.Decimal):
                return value
            elif isinstance(value, basestring):
                return decimal.Decimal(value)
            raise gae.BadValueError("Property %s must be a Decimal or string." % self.name)

###################################################################################
# class that handles connection pooling (all adapters are derived from this one)
###################################################################################

class ConnectionPool(object):

    pools = {}
    check_active_connection = True

    @staticmethod
    def set_folder(folder):
        thread.folder = folder

    # ## this allows gluon to commit/rollback all dbs in this thread

    @staticmethod
    def close_all_instances(action):
        """ to close cleanly databases in a multithreaded environment """
        if hasattr(thread, 'instances'):
            while thread.instances:
                instance = thread.instances.pop()
                if action:
                    if callable(action):
                        action(instance)
                    else:
                        getattr(instance, action)()
                # ## if you want pools, recycle this connection
                really = True
                if instance.pool_size:
                    sql_locker.acquire()
                    pool = ConnectionPool.pools[instance.uri]
                    if len(pool) < instance.pool_size:
                        pool.append(instance.connection)
                        really = False
                    sql_locker.release()
                if really:
                    getattr(instance, 'close')()

        if callable(action):
            action(None)
        return

    def find_or_make_work_folder(self):
        """ this actually does not make the folder. it has to be there """
        if hasattr(thread,'folder'):
            self.folder = thread.folder
        else:
            self.folder = thread.folder = ''

        # Creating the folder if it does not exist
        if False and self.folder and not os.path.exists(self.folder):
            os.mkdir(self.folder)

    def after_connection(self):
        """ this it is suppoed to be overloaded by adtapters"""
        pass

    def reconnect(self):
        """ allows a thread to re-connect to server or re-pool """
        self.close_all_instances(False)
        self.pool_connection(self._connection_function)
        self.after_connection()

    def pool_connection(self, f, cursor=True):
        """
        this function defines: self.connection and self.cursor (iff cursor is True)
        if self.pool_size>0 it will try pull the connection from the pool
        if the connection is not active (closed by db server) it will loop
        if not self.pool_size or no active connections in pool makes a new one
        """
        self._connection_function = f
        if not self.pool_size:
            self.connection = f()
            self.cursor = cursor and self.connection.cursor()
        else:
            uri = self.uri
            while True:
                sql_locker.acquire()
                if not uri in ConnectionPool.pools:
                    ConnectionPool.pools[uri] = []
                if ConnectionPool.pools[uri]:
                    self.connection = ConnectionPool.pools[uri].pop()
                    sql_locker.release()
                    self.cursor = cursor and self.connection.cursor()
                    try:
                        if self.cursor and self.check_active_connection:
                            self.execute('SELECT 1;')
                        break
                    except:
                        pass
                else:
                    sql_locker.release()
                    self.connection = f()
                    self.cursor = cursor and self.connection.cursor()
                    break
        if not hasattr(thread,'instances'):
            thread.instances = []
        thread.instances.append(self)


###################################################################################
# this is a generic adapter that does nothing; all others are derived from this one
###################################################################################

class BaseAdapter(ConnectionPool):

    driver = None
    maxcharlength = MAXCHARLENGTH
    commit_on_alter_table = False
    support_distributed_transaction = False
    uploads_in_blob = False
    can_select_for_update = True
    types = {
        'boolean': 'CHAR(1)',
        'string': 'CHAR(%(length)s)',
        'text': 'TEXT',
        'password': 'CHAR(%(length)s)',
        'blob': 'BLOB',
        'upload': 'CHAR(%(length)s)',
        'integer': 'INTEGER',
        'bigint': 'INTEGER',
        'float':'DOUBLE',
        'double': 'DOUBLE',
        'decimal': 'DOUBLE',
        'date': 'DATE',
        'time': 'TIME',
        'datetime': 'TIMESTAMP',
        'id': 'INTEGER PRIMARY KEY AUTOINCREMENT',
        'reference': 'INTEGER REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'list:integer': 'TEXT',
        'list:string': 'TEXT',
        'list:reference': 'TEXT',
        # the two below are only used when DAL(...bigint_id=True) and replace 'id','reference'
        'big-id': 'BIGINT PRIMARY KEY AUTOINCREMENT',
        'big-reference': 'BIGINT REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        }

    def adapt(self, obj):
        return "'%s'" % obj.replace("'", "''")

    def integrity_error(self):
        return self.driver.IntegrityError

    def operational_error(self):
        return self.driver.OperationalError

    def file_exists(self, filename):
        """
        to be used ONLY for files that on GAE may not be on filesystem
        """
        return os.path.exists(filename)

    def file_open(self, filename, mode='rb', lock=True):
        """
        to be used ONLY for files that on GAE may not be on filesystem
        """
        if have_portalocker and lock:
            fileobj = portalocker.LockedFile(filename,mode)
        else:
            fileobj = open(filename,mode)
        return fileobj

    def file_close(self, fileobj):
        """
        to be used ONLY for files that on GAE may not be on filesystem
        """
        if fileobj:
            fileobj.close()

    def file_delete(self, filename):
        os.unlink(filename)

    def __init__(self, db,uri,pool_size=0, folder=None, db_codec='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        self.db = db
        self.dbengine = "None"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        class Dummy(object):
            lastrowid = 1
            def __getattr__(self, value):
                return lambda *a, **b: []
        self.connection = Dummy()
        self.cursor = Dummy()

    def sequence_name(self,tablename):
        return '%s_sequence' % tablename

    def trigger_name(self,tablename):
        return '%s_sequence' % tablename

    def varquote(self,name):
        return name

    def create_table(self, table,
                     migrate=True,
                     fake_migrate=False,
                     polymodel=None):
        fields = []
        # PostGIS geo fields are added after the table has been created
        postcreation_fields = []
        sql_fields = {}
        sql_fields_aux = {}
        TFK = {}
        tablename = table._tablename
        sortable = 0
        for field in table:
            sortable += 1
            k = field.name
            if isinstance(field.type,SQLCustomType):
                ftype = field.type.native or field.type.type
            elif field.type.startswith('reference'):
                referenced = field.type[10:].strip()
                if referenced == '.':
                    referenced = tablename
                constraint_name = self.constraint_name(tablename, field.name)
                if not '.' in referenced \
                        and referenced != tablename \
                        and hasattr(table,'_primarykey'):
                    ftype = self.types['integer']
                else:
                    if hasattr(table,'_primarykey'):
                        rtablename,rfieldname = referenced.split('.')
                        rtable = table._db[rtablename]
                        rfield = rtable[rfieldname]
                        # must be PK reference or unique
                        if rfieldname in rtable._primarykey or rfield.unique:
                            ftype = self.types[rfield.type[:9]] % \
                                dict(length=rfield.length)
                            # multicolumn primary key reference?
                            if not rfield.unique and len(rtable._primarykey)>1:
                                # then it has to be a table level FK
                                if rtablename not in TFK:
                                    TFK[rtablename] = {}
                                TFK[rtablename][rfieldname] = field.name
                            else:
                                ftype = ftype + self.types['reference FK'] % dict(
                                    constraint_name = constraint_name, # should be quoted
                                    foreign_key = '%s (%s)' % (rtablename,
                                                               rfieldname),
                                    on_delete_action=field.ondelete)
                    else:
                        # make a guess here for circular references
                        id_fieldname = referenced in table._db \
                            and table._db[referenced]._id.name or 'id'
                        ftype = self.types[field.type[:9]] % dict( 
                            index_name = field.name+'__idx',
                            field_name = field.name,
                            constraint_name = constraint_name,
                            foreign_key = '%s (%s)' % (referenced,
                                                       id_fieldname),
                            on_delete_action=field.ondelete)
            elif field.type.startswith('list:reference'):
                ftype = self.types[field.type[:14]]
            elif field.type.startswith('decimal'):
                precision, scale = map(int,field.type[8:-1].split(','))
                ftype = self.types[field.type[:7]] % \
                    dict(precision=precision,scale=scale)
            elif field.type.startswith('geo'):
                srid = self.srid
                geotype, parms = field.type[:-1].split('(')
                if not geotype in self.types:
                    raise SyntaxError, 'Field: unknown field type: %s for %s' \
                        % (field.type, field.name)
                ftype = self.types[geotype]
                if self.dbengine == 'postgres' and geotype == 'geometry':
                    # parameters: schema, srid, dimension
                    dimension = 2 # GIS.dimension ???
                    parms = parms.split(',')
                    if len(parms) == 3:
                        schema, srid, dimension = parms
                    elif len(parms) == 2:
                        schema, srid = parms
                    else:
                        schema = parms[0]
                    ftype = "SELECT AddGeometryColumn ('%%(schema)s', '%%(tablename)s', '%%(fieldname)s', %%(srid)s, '%s', %%(dimension)s);" % self.types[geotype]
                    ftype = ftype % dict(schema=schema, tablename=tablename,
                            fieldname=field.name, srid=srid, dimension=dimension)
                    postcreation_fields.append(ftype)
            elif not field.type in self.types:
                raise SyntaxError, 'Field: unknown field type: %s for %s' % \
                    (field.type, field.name)
            else:
                ftype = self.types[field.type]\
                     % dict(length=field.length)
            if not field.type.startswith('id') and not field.type.startswith('reference'):
                if field.notnull:
                    ftype += ' NOT NULL'
                else:
                    ftype += self.ALLOW_NULL()
                if field.unique:
                    ftype += ' UNIQUE'
                if field.custom_qualifier:
                    ftype += ' %s' % field.custom_qualifier

            # add to list of fields
            sql_fields[field.name] = dict(sortable=sortable,
                                          type=str(field.type),
                                          sql=ftype)

            if isinstance(field.default,(str,int,float)):
                # Caveat: sql_fields and sql_fields_aux differ for default values.
                # sql_fields is used to trigger migrations and sql_fields_aux
                # is used for create tables.
                # The reason is that we do not want to trigger a migration simply
                # because a default value changes.
                not_null = self.NOT_NULL(field.default, field.type)
                ftype = ftype.replace('NOT NULL', not_null)
            sql_fields_aux[field.name] = dict(sql=ftype)
            # Postgres - PostGIS:
            # geometry fields are added after the table has been created, not now
            if not (self.dbengine == 'postgres' and field.type.startswith('geom')):
                fields.append('%s %s' % (field.name, ftype))
        other = ';'

        # backend-specific extensions to fields
        if self.dbengine == 'mysql':
            if not hasattr(table, "_primarykey"):
                fields.append('PRIMARY KEY(%s)' % table._id.name)
            other = ' ENGINE=InnoDB CHARACTER SET utf8;'

        fields = ',\n    '.join(fields)
        for rtablename in TFK:
            rfields = TFK[rtablename]
            pkeys = table._db[rtablename]._primarykey
            fkeys = [ rfields[k] for k in pkeys ]
            fields = fields + ',\n    ' + \
                     self.types['reference TFK'] % dict(
                table_name = tablename,
                field_name=', '.join(fkeys),
                foreign_table = rtablename,
                foreign_key = ', '.join(pkeys),
                on_delete_action = field.ondelete)

        if hasattr(table,'_primarykey'):
            query = "CREATE TABLE %s(\n    %s,\n    %s) %s" % \
                (tablename, fields, self.PRIMARY_KEY(', '.join(table._primarykey)),other)
        else:
            query = "CREATE TABLE %s(\n    %s\n)%s" % \
                (tablename, fields, other)

        if self.uri.startswith('sqlite:///') or self.uri.startswith('spatialite:///'):
            path_encoding = sys.getfilesystemencoding() or locale.getdefaultlocale()[1] or 'utf8'
            dbpath = self.uri[9:self.uri.rfind('/')].decode('utf8').encode(path_encoding)
        else:
            dbpath = self.folder

        if not migrate:
            return query
        elif self.uri.startswith('sqlite:memory') or self.uri.startswith('spatialite:memory'):
            table._dbt = None
        elif isinstance(migrate, str):
            table._dbt = os.path.join(dbpath, migrate)
        else:
            table._dbt = os.path.join(dbpath, '%s_%s.table' \
                                          % (table._db._uri_hash, tablename))
        if table._dbt:
            table._loggername = os.path.join(dbpath, 'sql.log')
            logfile = self.file_open(table._loggername, 'a')
        else:
            logfile = None
        if not table._dbt or not self.file_exists(table._dbt):
            if table._dbt:
                logfile.write('timestamp: %s\n'
                               % datetime.datetime.today().isoformat())
                logfile.write(query + '\n')
            if not fake_migrate:
                self.create_sequence_and_triggers(query,table)
                table._db.commit()
                # Postgres geom fields are added now, after the table has been created
                for query in postcreation_fields:
                    self.execute(query)
                    table._db.commit()
            if table._dbt:
                tfile = self.file_open(table._dbt, 'w')
                cPickle.dump(sql_fields, tfile)
                self.file_close(tfile)
                if fake_migrate:
                    logfile.write('faked!\n')
                else:
                    logfile.write('success!\n')
        else:
            tfile = self.file_open(table._dbt, 'r')
            try:
                sql_fields_old = cPickle.load(tfile)
            except EOFError:
                self.file_close(tfile)
                self.file_close(logfile)
                raise RuntimeError, 'File %s appears corrupted' % table._dbt
            self.file_close(tfile)
            if sql_fields != sql_fields_old:
                self.migrate_table(table,
                                   sql_fields, sql_fields_old,
                                   sql_fields_aux, logfile,
                                   fake_migrate=fake_migrate)
        self.file_close(logfile)
        return query

    def migrate_table(
        self,
        table,
        sql_fields,
        sql_fields_old,
        sql_fields_aux,
        logfile,
        fake_migrate=False,
        ):
        table._db._migrated.append(table._tablename)
        tablename = table._tablename
        def fix(item):
            k,v=item
            if not isinstance(v,dict):
                v=dict(type='unkown',sql=v)
            return k.lower(),v
        ### make sure all field names are lower case to avoid conflicts
        sql_fields = dict(map(fix,sql_fields.items()))
        sql_fields_old = dict(map(fix,sql_fields_old.items()))
        sql_fields_aux = dict(map(fix,sql_fields_aux.items()))

        keys = sql_fields.keys()
        for key in sql_fields_old:
            if not key in keys:
                keys.append(key)
        if self.dbengine == 'mssql':
            new_add = '; ALTER TABLE %s ADD ' % tablename
        else:
            new_add = ', ADD '

        metadata_change = False
        sql_fields_current = copy.copy(sql_fields_old)
        for key in keys:
            query = None
            if not key in sql_fields_old:
                sql_fields_current[key] = sql_fields[key]
                if self.dbengine in ('postgres',) and \
                   sql_fields[key]['type'].startswith('geometry'):
                    # 'sql' == ftype in sql
                    query = [ sql_fields[key]['sql'] ]
                else:
                    query = ['ALTER TABLE %s ADD %s %s;' % \
                         (tablename, key,
                          sql_fields_aux[key]['sql'].replace(', ', new_add))]
                metadata_change = True
            elif self.dbengine in ('sqlite', 'spatialite'):
                if key in sql_fields:
                    sql_fields_current[key] = sql_fields[key]
                metadata_change = True
            elif not key in sql_fields:
                del sql_fields_current[key]
                ftype = sql_fields_old[key]['type']
                if self.dbengine in ('postgres',) and ftype.startswith('geometry'):
                    geotype, parms = ftype[:-1].split('(')
                    schema = parms.split(',')[0]
                    query = [ "SELECT DropGeometryColumn ('%(schema)s', '%(table)s', '%(field)s');" % \
                        dict(schema=schema, table=tablename, field=key,) ]
                elif not self.dbengine in ('firebird',):
                    query = ['ALTER TABLE %s DROP COLUMN %s;' % (tablename, key)]
                else:
                    query = ['ALTER TABLE %s DROP %s;' % (tablename, key)]
                metadata_change = True
            elif sql_fields[key]['sql'] != sql_fields_old[key]['sql'] \
                  and not isinstance(table[key].type, SQLCustomType) \
                  and not table[key].type.startswith('reference')\
                  and not table[key].type.startswith('double')\
                  and not table[key].type.startswith('id'):
                sql_fields_current[key] = sql_fields[key]
                t = tablename
                tt = sql_fields_aux[key]['sql'].replace(', ', new_add)
                if not self.dbengine in ('firebird',):
                    query = ['ALTER TABLE %s ADD %s__tmp %s;' % (t, key, tt),
                             'UPDATE %s SET %s__tmp=%s;' % (t, key, key),
                             'ALTER TABLE %s DROP COLUMN %s;' % (t, key),
                             'ALTER TABLE %s ADD %s %s;' % (t, key, tt),
                             'UPDATE %s SET %s=%s__tmp;' % (t, key, key),
                             'ALTER TABLE %s DROP COLUMN %s__tmp;' % (t, key)]
                else:
                    query = ['ALTER TABLE %s ADD %s__tmp %s;' % (t, key, tt),
                             'UPDATE %s SET %s__tmp=%s;' % (t, key, key),
                             'ALTER TABLE %s DROP %s;' % (t, key),
                             'ALTER TABLE %s ADD %s %s;' % (t, key, tt),
                             'UPDATE %s SET %s=%s__tmp;' % (t, key, key),
                             'ALTER TABLE %s DROP %s__tmp;' % (t, key)]
                metadata_change = True
            elif sql_fields[key]['type'] != sql_fields_old[key]['type']:
                sql_fields_current[key] = sql_fields[key]
                metadata_change = True

            if query:
                logfile.write('timestamp: %s\n'
                              % datetime.datetime.today().isoformat())
                table._db['_lastsql'] = '\n'.join(query)
                for sub_query in query:
                    logfile.write(sub_query + '\n')
                    if not fake_migrate:
                        self.execute(sub_query)
                        # Caveat: mysql, oracle and firebird do not allow multiple alter table
                        # in one transaction so we must commit partial transactions and
                        # update table._dbt after alter table.
                        if table._db._adapter.commit_on_alter_table:
                            table._db.commit()
                            tfile = self.file_open(table._dbt, 'w')
                            cPickle.dump(sql_fields_current, tfile)
                            self.file_close(tfile)
                            logfile.write('success!\n')
                    else:
                        logfile.write('faked!\n')
            elif metadata_change:
                tfile = self.file_open(table._dbt, 'w')
                cPickle.dump(sql_fields_current, tfile)
                self.file_close(tfile)

        if metadata_change and \
                not (query and self.dbengine in ('mysql','oracle','firebird')):
            table._db.commit()
            tfile = self.file_open(table._dbt, 'w')
            cPickle.dump(sql_fields_current, tfile)
            self.file_close(tfile)

    def LOWER(self, first):
        return 'LOWER(%s)' % self.expand(first)

    def UPPER(self, first):
        return 'UPPER(%s)' % self.expand(first)

    def COUNT(self, first, distinct=None):
        return ('COUNT(%s)' if not distinct else 'COUNT(DISTINCT %s)') \
            % self.expand(first)

    def EXTRACT(self, first, what):
        return "EXTRACT(%s FROM %s)" % (what, self.expand(first))

    def AGGREGATE(self, first, what):
        return "%s(%s)" % (what, self.expand(first))

    def JOIN(self):
        return 'JOIN'

    def LEFT_JOIN(self):
        return 'LEFT JOIN'

    def RANDOM(self):
        return 'Random()'

    def NOT_NULL(self, default, field_type):
        return 'NOT NULL DEFAULT %s' % self.represent(default,field_type)

    def COALESCE(self, first, second):
        expressions = [self.expand(first)]+[self.expand(e) for e in second]
        return 'COALESCE(%s)' % ','.join(expressions)

    def COALESCE_ZERO(self, first):
        return 'COALESCE(%s,0)' % self.expand(first)

    def RAW(self, first):
        return first

    def ALLOW_NULL(self):
        return ''

    def SUBSTRING(self, field, parameters):
        return 'SUBSTR(%s,%s,%s)' % (self.expand(field), parameters[0], parameters[1])

    def PRIMARY_KEY(self, key):
        return 'PRIMARY KEY(%s)' % key

    def _drop(self, table, mode):
        return ['DROP TABLE %s;' % table]

    def drop(self, table, mode=''):
        if table._dbt:
            logfile = self.file_open(table._loggername, 'a')
        queries = self._drop(table, mode)
        for query in queries:
            if table._dbt:
                logfile.write(query + '\n')
            self.execute(query)
        table._db.commit()
        del table._db[table._tablename]
        del table._db.tables[table._db.tables.index(table._tablename)]
        table._db._update_referenced_by(table._tablename)
        if table._dbt:
            self.file_delete(table._dbt)
            logfile.write('success!\n')

    def _insert(self, table, fields):
        keys = ','.join(f.name for f,v in fields)
        values = ','.join(self.expand(v,f.type) for f,v in fields)
        return 'INSERT INTO %s(%s) VALUES (%s);' % (table, keys, values)

    def insert(self, table, fields):
        query = self._insert(table,fields)
        try:
            self.execute(query)
        except Exception, e:
            if isinstance(e,self.integrity_error_class()):
                return None
            raise e
        if hasattr(table,'_primarykey'):
            return dict([(k[0].name, k[1]) for k in fields \
                             if k[0].name in table._primarykey])
        id = self.lastrowid(table)
        if not isinstance(id,int):
            return id
        rid = Reference(id)
        (rid._table, rid._record) = (table, None)
        return rid

    def bulk_insert(self, table, items):
        return [self.insert(table,item) for item in items]

    def NOT(self, first):
        return '(NOT %s)' % self.expand(first)

    def AND(self, first, second):
        return '(%s AND %s)' % (self.expand(first), self.expand(second))

    def OR(self, first, second):
        return '(%s OR %s)' % (self.expand(first), self.expand(second))

    def BELONGS(self, first, second):
        if isinstance(second, str):
            return '(%s IN (%s))' % (self.expand(first), second[:-1])
        elif second==[] or second==():
            return '(1=0)'
        items = ','.join(self.expand(item, first.type) for item in second)
        return '(%s IN (%s))' % (self.expand(first), items)

    def REGEXP(self, first, second):
        "regular expression operator"
        raise NotImplementedError

    def LIKE(self, first, second):
        "case sensitive like operator"
        raise NotImplementedError

    def ILIKE(self, first, second):
        "case in-sensitive like operator"
        return '(%s LIKE %s)' % (self.expand(first), self.expand(second, 'string'))

    def STARTSWITH(self, first, second):
        return '(%s LIKE %s)' % (self.expand(first), self.expand(second+'%', 'string'))

    def ENDSWITH(self, first, second):
        return '(%s LIKE %s)' % (self.expand(first), self.expand('%'+second, 'string'))

    def CONTAINS(self, first, second):
        if first.type in ('string', 'text'):
            key = '%'+str(second).replace('%','%%')+'%'
        elif first.type.startswith('list:'):
            key = '%|'+str(second).replace('|','||').replace('%','%%')+'|%'
        return '(%s LIKE %s)' % (self.expand(first),self.expand(key,'string'))

    def EQ(self, first, second=None):
        if second is None:
            return '(%s IS NULL)' % self.expand(first)
        return '(%s = %s)' % (self.expand(first), self.expand(second, first.type))

    def NE(self, first, second=None):
        if second is None:
            return '(%s IS NOT NULL)' % self.expand(first)
        return '(%s <> %s)' % (self.expand(first), self.expand(second, first.type))

    def LT(self,first,second=None):
        if second is None:
            raise RuntimeError, "Cannot compare %s < None" % first
        return '(%s < %s)' % (self.expand(first),self.expand(second,first.type))

    def LE(self,first,second=None):
        if second is None:
            raise RuntimeError, "Cannot compare %s <= None" % first
        return '(%s <= %s)' % (self.expand(first),self.expand(second,first.type))

    def GT(self,first,second=None):
        if second is None:
            raise RuntimeError, "Cannot compare %s > None" % first
        return '(%s > %s)' % (self.expand(first),self.expand(second,first.type))

    def GE(self,first,second=None):
        if second is None:
            raise RuntimeError, "Cannot compare %s >= None" % first
        return '(%s >= %s)' % (self.expand(first),self.expand(second,first.type))

    def ADD(self, first, second):
        return '(%s + %s)' % (self.expand(first), self.expand(second, first.type))

    def SUB(self, first, second):
        return '(%s - %s)' % (self.expand(first), self.expand(second, first.type))

    def MUL(self, first, second):
        return '(%s * %s)' % (self.expand(first), self.expand(second, first.type))

    def DIV(self, first, second):
        return '(%s / %s)' % (self.expand(first), self.expand(second, first.type))

    def MOD(self, first, second):
        return '(%s %% %s)' % (self.expand(first), self.expand(second, first.type))

    def AS(self, first, second):
        return '%s AS %s' % (self.expand(first), second)

    def ON(self, first, second):
        return '%s ON %s' % (self.expand(first), self.expand(second))

    def INVERT(self, first):
        return '%s DESC' % self.expand(first)

    def COMMA(self, first, second):
        return '%s, %s' % (self.expand(first), self.expand(second))

    def expand(self, expression, field_type=None):
        if isinstance(expression, Field):
            return '%s.%s' % (expression.tablename, expression.name)
        elif isinstance(expression, (Expression, Query)):
            if not expression.second is None:
                return expression.op(expression.first, expression.second)
            elif not expression.first is None:
                return expression.op(expression.first)
            elif not isinstance(expression.op, str):
                return expression.op()
            else:
                op = expression.op
                if op.endswith(';'): op=op[:-1]
                return '(%s)' % op
        elif field_type:
            return str(self.represent(expression,field_type))
        elif isinstance(expression,(list,tuple)):
            return ','.join(self.represent(item,field_type) for item in expression)
        elif isinstance(expression, bool):
            return '1' if expression else '0'
        else:
            return str(expression)

    def alias(self, table, alias):
        """
        Given a table object, makes a new table object
        with alias name.
        """
        other = copy.copy(table)
        other['_ot'] = other._tablename
        other['ALL'] = SQLALL(other)
        other['_tablename'] = alias
        for fieldname in other.fields:
            other[fieldname] = copy.copy(other[fieldname])
            other[fieldname]._tablename = alias
            other[fieldname].tablename = alias
            other[fieldname].table = other
        table._db[alias] = other
        return other

    def _truncate(self, table, mode=''):
        tablename = table._tablename
        return ['TRUNCATE TABLE %s %s;' % (tablename, mode or '')]

    def truncate(self, table, mode= ' '):
        # Prepare functions "write_to_logfile" and "close_logfile"
        if table._dbt:
            logfile = self.file_open(table._loggername, 'a')
        else:
            class Logfile(object):
                def write(self, value):
                    pass
                def close(self):
                    pass
            logfile = Logfile()

        try:
            queries = table._db._adapter._truncate(table, mode)
            for query in queries:
                logfile.write(query + '\n')
                self.execute(query)
            table._db.commit()
            logfile.write('success!\n')
        finally:
            logfile.close()

    def _update(self, tablename, query, fields):
        if query:
            if use_common_filters(query):
                query = self.common_filter(query, [tablename])
            sql_w = ' WHERE ' + self.expand(query)
        else:
            sql_w = ''
        sql_v = ','.join(['%s=%s' % (field.name, self.expand(value, field.type)) \
                              for (field, value) in fields])
        return 'UPDATE %s SET %s%s;' % (tablename, sql_v, sql_w)

    def update(self, tablename, query, fields):
        sql = self._update(tablename, query, fields)
        self.execute(sql)
        try:
            return self.cursor.rowcount
        except:
            return None

    def _delete(self, tablename, query):
        if query:
            if use_common_filters(query):
                query = self.common_filter(query, [tablename])
            sql_w = ' WHERE ' + self.expand(query)
        else:
            sql_w = ''
        return 'DELETE FROM %s%s;' % (tablename, sql_w)

    def delete(self, tablename, query):
        sql = self._delete(tablename, query)
        ### special code to handle CASCADE in SQLite & SpatiaLite
        db = self.db
        table = db[tablename]
        if self.dbengine in ('sqlite', 'spatialite') and table._referenced_by:
            deleted = [x[table._id.name] for x in db(query).select(table._id)]
        ### end special code to handle CASCADE in SQLite & SpatiaLite
        self.execute(sql)
        try:
            counter = self.cursor.rowcount
        except:
            counter =  None
        ### special code to handle CASCADE in SQLite & SpatiaLite
        if self.dbengine in ('sqlite', 'spatialite') and counter:
            for tablename,fieldname in table._referenced_by:
                f = db[tablename][fieldname]
                if f.type=='reference '+table._tablename and f.ondelete=='CASCADE':
                    db(db[tablename][fieldname].belongs(deleted)).delete()
        ### end special code to handle CASCADE in SQLite & SpatiaLite
        return counter

    def get_table(self, query):
        tablenames = self.tables(query)
        if len(tablenames)==1:
            return tablenames[0]
        elif len(tablenames)<1:
            raise RuntimeError, "No table selected"
        else:
            raise RuntimeError, "Too many tables selected"

    def expand_all(self, fields, tablenames):
        new_fields = []
        for item in fields:
            if isinstance(item,SQLALL):
                new_fields += item._table
            else:
                new_fields.append(item)
        # ## if no fields specified take them all from the requested tables
        if not new_fields:
            for table in tablenames:
                for field in self.db[table]:
                    new_fields.append(field)
        return new_fields

    def _select(self, query, fields, attributes):
        for key in set(attributes.keys())-set(('orderby', 'groupby', 'limitby',
                                               'required', 'cache', 'left',
                                               'distinct', 'having', 'join',
                                               'for_update', 'processor')):
            raise SyntaxError, 'invalid select attribute: %s' % key

        tablenames = self.tables(query)
        for field in fields:
            if isinstance(field, basestring) and regex_table_field.match(field):
                tn,fn = field.split('.')
                field = self.db[tn][fn]
            for tablename in self.tables(field):
                if not tablename in tablenames:
                    tablenames.append(tablename)

        if use_common_filters(query):
            query = self.common_filter(query,tablenames)

        if len(tablenames) < 1:
            raise SyntaxError, 'Set: no tables selected'
        sql_f = ', '.join(map(self.expand, fields))
        self._colnames = [c.strip() for c in sql_f.split(', ')]
        if query:
            sql_w = ' WHERE ' + self.expand(query)
        else:
            sql_w = ''
        sql_o = ''
        sql_s = ''
        left = attributes.get('left', False)
        inner_join = attributes.get('join', False)
        distinct = attributes.get('distinct', False)
        groupby = attributes.get('groupby', False)
        orderby = attributes.get('orderby', False)
        having = attributes.get('having', False)
        limitby = attributes.get('limitby', False)
        for_update = attributes.get('for_update', False)
        if self.can_select_for_update is False and for_update is True:
            raise SyntaxError, 'invalid select attribute: for_update'
        if distinct is True:
            sql_s += 'DISTINCT'
        elif distinct:
            sql_s += 'DISTINCT ON (%s)' % distinct
        if inner_join:
            icommand = self.JOIN()
            if not isinstance(inner_join, (tuple, list)):
                inner_join = [inner_join]
            ijoint = [t._tablename for t in inner_join if not isinstance(t,Expression)]
            ijoinon = [t for t in inner_join if isinstance(t, Expression)]
            itables_to_merge={} #issue 490
            [itables_to_merge.update(dict.fromkeys(self.tables(t))) for t in ijoinon] # issue 490
            ijoinont = [t.first._tablename for t in ijoinon]
            [itables_to_merge.pop(t) for t in ijoinont if t in itables_to_merge] #issue 490
            iimportant_tablenames = ijoint + ijoinont + itables_to_merge.keys() # issue 490
            iexcluded = [t for t in tablenames if not t in iimportant_tablenames]
        if left:
            join = attributes['left']
            command = self.LEFT_JOIN()
            if not isinstance(join, (tuple, list)):
                join = [join]
            joint = [t._tablename for t in join if not isinstance(t, Expression)]
            joinon = [t for t in join if isinstance(t, Expression)]
            #patch join+left patch (solves problem with ordering in left joins)
            tables_to_merge={}
            [tables_to_merge.update(dict.fromkeys(self.tables(t))) for t in joinon]
            joinont = [t.first._tablename for t in joinon]
            [tables_to_merge.pop(t) for t in joinont if t in tables_to_merge]
            important_tablenames = joint + joinont + tables_to_merge.keys()
            excluded = [t for t in tablenames if not t in important_tablenames ]
        def alias(t):
            return str(self.db[t])
        if inner_join and not left:
            sql_t = ', '.join([alias(t) for t in iexcluded + itables_to_merge.keys()]) # issue 490
            for t in ijoinon:
                sql_t += ' %s %s' % (icommand, str(t))
        elif not inner_join and left:
            sql_t = ', '.join([alias(t) for t in excluded + tables_to_merge.keys()])
            if joint:
                sql_t += ' %s %s' % (command, ','.join([t for t in joint]))
            for t in joinon:
                sql_t += ' %s %s' % (command, str(t))
        elif inner_join and left:
            all_tables_in_query = set(important_tablenames + \
                                      iimportant_tablenames + \
                                      tablenames) # issue 490
            tables_in_joinon = set(joinont + ijoinont) # issue 490
            tables_not_in_joinon = all_tables_in_query.difference(tables_in_joinon) # issue 490
            sql_t = ','.join([alias(t) for t in tables_not_in_joinon]) # issue 490
            for t in ijoinon:
                sql_t += ' %s %s' % (icommand, str(t))
            if joint:
                sql_t += ' %s %s' % (command, ','.join([t for t in joint]))
            for t in joinon:
                sql_t += ' %s %s' % (command, str(t))
        else:
            sql_t = ', '.join(alias(t) for t in tablenames)
        if groupby:
            if isinstance(groupby, (list, tuple)):
                groupby = xorify(groupby)
            sql_o += ' GROUP BY %s' % self.expand(groupby)
            if having:
                sql_o += ' HAVING %s' % attributes['having']
        if orderby:
            if isinstance(orderby, (list, tuple)):
                orderby = xorify(orderby)
            if str(orderby) == '<random>':
                sql_o += ' ORDER BY %s' % self.RANDOM()
            else:
                sql_o += ' ORDER BY %s' % self.expand(orderby)
        if limitby:
            if not orderby and tablenames:
                sql_o += ' ORDER BY %s' % ', '.join(['%s.%s'%(t,x) for t in tablenames for x in ((hasattr(self.db[t], '_primarykey') and self.db[t]._primarykey) or [self.db[t]._id.name])])
            # oracle does not support limitby
        sql = self.select_limitby(sql_s, sql_f, sql_t, sql_w, sql_o, limitby)
        if for_update and self.can_select_for_update is True:
            sql = sql.rstrip(';') + ' FOR UPDATE;'
        return sql

    def select_limitby(self, sql_s, sql_f, sql_t, sql_w, sql_o, limitby):
        if limitby:
            (lmin, lmax) = limitby
            sql_o += ' LIMIT %i OFFSET %i' % (lmax - lmin, lmin)
        return 'SELECT %s %s FROM %s%s%s;' % (sql_s, sql_f, sql_t, sql_w, sql_o)

    def select(self, query, fields, attributes):
        """
        Always returns a Rows object, possibly empty.
        """
        def response(sql):
            self.execute(sql)
            return self.cursor.fetchall()
        sql = self._select(query, fields, attributes)
        if attributes.get('cache', None):
            (cache_model, time_expire) = attributes['cache']
            del attributes['cache']
            key = self.uri + '/' + sql
            key = (len(key)<=200) and key or hashlib.md5(key).hexdigest()
            rows = cache_model(key, lambda: response(sql), time_expire)
        else:
            rows = response(sql)
        if isinstance(rows,tuple):
            rows = list(rows)
        limitby = attributes.get('limitby', None) or (0,)
        rows = self.rowslice(rows,limitby[0],None)
        processor = attributes.get('processor',self.parse)
        return processor(rows,fields,self._colnames)

    def _count(self, query, distinct=None):
        tablenames = self.tables(query)
        if query:
            if use_common_filters(query):
                query = self.common_filter(query, tablenames)
            sql_w = ' WHERE ' + self.expand(query)
        else:
            sql_w = ''
        sql_t = ','.join(tablenames)
        if distinct:
            if isinstance(distinct,(list, tuple)):
                distinct = xorify(distinct)
            sql_d = self.expand(distinct)
            return 'SELECT count(DISTINCT %s) FROM %s%s;' % (sql_d, sql_t, sql_w)
        return 'SELECT count(*) FROM %s%s;' % (sql_t, sql_w)

    def count(self, query, distinct=None):
        self.execute(self._count(query, distinct))
        return self.cursor.fetchone()[0]

    def tables(self, query):
        tables = set()
        if isinstance(query, Field):
            tables.add(query.tablename)
        elif isinstance(query, (Expression, Query)):
            if not query.first is None:
                tables = tables.union(self.tables(query.first))
            if not query.second is None:
                tables = tables.union(self.tables(query.second))
        return list(tables)

    def commit(self):
        return self.connection.commit()

    def rollback(self):
        return self.connection.rollback()

    def close(self):
        return self.connection.close()

    def distributed_transaction_begin(self, key):
        return

    def prepare(self, key):
        self.connection.prepare()

    def commit_prepared(self, key):
        self.connection.commit()

    def rollback_prepared(self, key):
        self.connection.rollback()

    def concat_add(self, table):
        return ', ADD '

    def constraint_name(self, table, fieldname):
        return '%s_%s__constraint' % (table,fieldname)

    def create_sequence_and_triggers(self, query, table, **args):
        self.execute(query)

    def log_execute(self, *a, **b):
        command = a[0]
        if self.db._debug:
            logger.debug('SQL: %s' % command)
        self.db._lastsql = command
        t0 = time.time()
        ret = self.cursor.execute(*a, **b)
        self.db._timings.append((command,time.time()-t0))
        del self.db._timings[:-TIMINGSSIZE]
        return ret

    def execute(self, *a, **b):
        return self.log_execute(*a, **b)

    def represent(self, obj, fieldtype):
        if isinstance(obj, CALLABLETYPES):
            obj = obj()
        if isinstance(fieldtype, SQLCustomType):
            value = fieldtype.encoder(obj)
            if fieldtype.type in ('string','text'):
                return self.adapt(value)
            return value
        if isinstance(obj, (Expression, Field)):
            return str(obj)
        if fieldtype.startswith('list:'):
            if not obj:
                obj = []
            elif not isinstance(obj, (list, tuple)):
                obj = [obj]
            if fieldtype.startswith('list:string'):
                obj = [str(item) for item in obj]
            else:
                obj = [int(item) for item in obj]
        if isinstance(obj, (list, tuple)):
            obj = bar_encode(obj)
        if obj is None:
            return 'NULL'
        if obj == '' and not fieldtype[:2] in ['st', 'te', 'pa', 'up']:
            return 'NULL'
        r = self.represent_exceptions(obj, fieldtype)
        if not r is None:
            return r
        if fieldtype == 'boolean':
            if obj and not str(obj)[:1].upper() in ['F', '0']:
                return "'T'"
            else:
                return "'F'"
        if fieldtype == 'id' or fieldtype == 'integer':
            return str(int(obj))
        if fieldtype.startswith('decimal'):
            return str(obj)
        elif fieldtype.startswith('reference'): # reference
            if fieldtype.find('.')>0:
                return repr(obj)
            elif isinstance(obj, (Row, Reference)):
                return str(obj['id'])
            return str(int(obj))
        elif fieldtype == 'double':
            return repr(float(obj))
        if isinstance(obj, unicode):
            obj = obj.encode(self.db_codec)
        if fieldtype == 'blob':
            obj = base64.b64encode(str(obj))
        elif fieldtype == 'date':
            if isinstance(obj, (datetime.date, datetime.datetime)):
                obj = obj.isoformat()[:10]
            else:
                obj = str(obj)
        elif fieldtype == 'datetime':
            if isinstance(obj, datetime.datetime):
                obj = obj.isoformat()[:19].replace('T',' ')
            elif isinstance(obj, datetime.date):
                obj = obj.isoformat()[:10]+' 00:00:00'
            else:
                obj = str(obj)
        elif fieldtype == 'time':
            if isinstance(obj, datetime.time):
                obj = obj.isoformat()[:10]
            else:
                obj = str(obj)
        if not isinstance(obj,str):
            obj = str(obj)
        try:
            obj.decode(self.db_codec)
        except:
            obj = obj.decode('latin1').encode(self.db_codec)
        return self.adapt(obj)

    def represent_exceptions(self, obj, fieldtype):
        return None

    def lastrowid(self, table):
        return None

    def integrity_error_class(self):
        return type(None)

    def rowslice(self, rows, minimum=0, maximum=None):
        """ By default this function does nothing; overload when db does not do slicing. """
        return rows

    def parse_value(self, value, field_type, blob_decode=True):
        if field_type != 'blob' and isinstance(value, str):
            try:
                value = value.decode(self.db._db_codec)
            except Exception:
                pass
        if isinstance(value, unicode):
            value = value.encode('utf-8')
        if isinstance(field_type, SQLCustomType):
            value = field_type.decoder(value)
        if not isinstance(field_type, str) or value is None:
            return value
        elif field_type in ('string', 'text', 'password', 'upload', 'dict'): # ???
            return value
        elif field_type.startswith('geo'):
            return value
        elif field_type == 'blob' and not blob_decode:
            return value
        else:
            key = regex_type.match(field_type).group(0)
            return self.parsemap[key](value,field_type)

    def parse_reference(self, value, field_type):
        referee = field_type[10:].strip()
        if not '.' in referee:
            value = Reference(value)
            value._table, value._record = self.db[referee], None
        return value

    def parse_boolean(self, value, field_type):
        return value == True or str(value)[:1].lower() == 't'

    def parse_date(self, value, field_type):
        if not isinstance(value, (datetime.date,datetime.datetime)):
            (y, m, d) = map(int, str(value)[:10].strip().split('-'))
            value = datetime.date(y, m, d)
        return value

    def parse_time(self, value, field_type):
        if not isinstance(value, datetime.time):
            time_items = map(int,str(value)[:8].strip().split(':')[:3])
            if len(time_items) == 3:
                (h, mi, s) = time_items
            else:
                (h, mi, s) = time_items + [0]
            value = datetime.time(h, mi, s)
        return value

    def parse_datetime(self, value, field_type):
        if not isinstance(value, datetime.datetime):
            date_part, time_part = (str(value).replace('T',' ')+' ').split(' ',1)
            (y, m, d) = map(int,date_part.split('-'))
            time_parts = time_part and time_part.split(':')[:3] or (0,0,0)
            while len(time_parts)<3: time_parts.append(0)
            time_items = map(int,time_parts)
            (h, mi, s) = time_items
            value = datetime.datetime(y, m, d, h, mi, s)
        return value

    def parse_blob(self, value, field_type):
        return base64.b64decode(str(value))

    def parse_decimal(self, value, field_type):
        decimals = int(field_type[8:-1].split(',')[-1])
        if self.dbengine in ('sqlite', 'spatialite'):
            value = ('%.' + str(decimals) + 'f') % value
        if not isinstance(value, decimal.Decimal):
            value = decimal.Decimal(str(value))
        return value

    def parse_list_integers(self, value, field_type):
        if not self.dbengine=='google:datastore':
            value = bar_decode_integer(value)
        return value

    def parse_list_references(self, value, field_type):
        if not self.dbengine=='google:datastore':
            value = bar_decode_integer(value)
        return [self.parse_reference(r, field_type[5:]) for r in value]

    def parse_list_strings(self, value, field_type):
        if not self.dbengine=='google:datastore':
            value = bar_decode_string(value)
        return value

    def parse_id(self, value, field_type):
        return int(value)

    def parse_integer(self, value, field_type):
        return int(value)

    def parse_double(self, value, field_type):
        return float(value)

    def build_parsemap(self):
        self.parsemap = {
            'id':self.parse_id,
            'integer':self.parse_integer,
            'bigint':self.parse_integer,
            'float':self.parse_double,
            'double':self.parse_double,
            'reference':self.parse_reference,
            'boolean':self.parse_boolean,
            'date':self.parse_date,
            'time':self.parse_time,
            'datetime':self.parse_datetime,
            'blob':self.parse_blob,
            'decimal':self.parse_decimal,
            'list:integer':self.parse_list_integers,
            'list:reference':self.parse_list_references,
            'list:string':self.parse_list_strings,
            }

    def parse(self, rows, fields, colnames, blob_decode=True):
        self.build_parsemap()
        db = self.db
        virtualtables = []
        new_rows = []
        for (i,row) in enumerate(rows):
            new_row = Row()
            for j,colname in enumerate(colnames):
                value = row[j]
                if not regex_table_field.match(colnames[j]):
                    if not '_extra' in new_row:
                        new_row['_extra'] = Row()
                    new_row['_extra'][colnames[j]] = \
                        self.parse_value(value, fields[j].type,blob_decode)
                    new_column_name = \
                        regex_select_as_parser.search(colnames[j])
                    if not new_column_name is None:
                        column_name = new_column_name.groups(0)
                        setattr(new_row,column_name[0],value)
                else:
                    (tablename, fieldname) = colname.split('.')
                    table = db[tablename]
                    field = table[fieldname]
                    if not tablename in new_row:
                        colset = new_row[tablename] = Row()
                        if tablename not in virtualtables:
                            virtualtables.append(tablename)
                    else:
                        colset = new_row[tablename]
                    value = self.parse_value(value,field.type,blob_decode)
                    if field.filter_out: value = field.filter_out(value)
                    colset[fieldname] = value

                    if field.type == 'id':
                        # temporary hack to deal with GoogleDatastoreAdapter
                        # references
                        if isinstance(self, GoogleDatastoreAdapter):
                            id = value.key().id_or_name()
                            colset[fieldname] = id
                            colset.gae_item = value
                        else:
                            id = value
                        colset.update_record = lambda _ = (colset, table, id), **a: update_record(_, a)
                        colset.delete_record = lambda t = table, i = id: t._db(t._id==i).delete()
                        for (referee_table, referee_name) in table._referenced_by:
                            s = db[referee_table][referee_name]
                            referee_link = db._referee_name and \
                                db._referee_name % dict(table=referee_table,field=referee_name)
                            if referee_link and not referee_link in colset:
                                colset[referee_link] = Set(db, s == id)
            new_rows.append(new_row)
        rowsobj = Rows(db, new_rows, colnames, rawrows=rows)

        for tablename in virtualtables:
            ### new style virtual fields
            table = db[tablename]
            fields_virtual = [(f,v) for (f,v) in table.items() if isinstance(v,FieldVirtual)]
            fields_lazy = [(f,v) for (f,v) in table.items() if isinstance(v,FieldLazy)]
            if fields_virtual or fields_lazy:
                for row in rowsobj.records:
                    box = row[tablename]
                    for f,v in fields_virtual:
                        box[f] = v.f(row)
                    for f,v in fields_lazy:
                        box[f] = (v.handler or VirtualCommand)(v.f,row)

            ### old style virtual fields
            for item in table.virtualfields:
                try:
                    rowsobj = rowsobj.setvirtualfields(**{tablename:item})
                except KeyError:
                    # to avoid breaking virtualfields when partial select
                    pass
        return rowsobj

    def common_filter(self, query, tablenames):
        tenant_fieldname = self.db._request_tenant

        for tablename in tablenames:
            table = self.db[tablename]

            # deal with user provided filters
            if table._common_filter != None:
                query = query & table._common_filter(query)

            # deal with multi_tenant filters
            if tenant_fieldname in table:
                default = table[tenant_fieldname].default
                if not default is None:
                    newquery = table[tenant_fieldname] == default
                    if query is None:
                        query = newquery
                    else:
                        query = query & newquery
        return query


###################################################################################
# List of all the available adapters; they all extend BaseAdapter.
###################################################################################

class SQLiteAdapter(BaseAdapter):

    driver = globals().get('sqlite3', None)
    can_select_for_update = None    # support ourselves with BEGIN TRANSACTION

    def EXTRACT(self,field,what):
        return "web2py_extract('%s',%s)" % (what, self.expand(field))

    @staticmethod
    def web2py_extract(lookup, s):
        table = {
            'year': (0, 4),
            'month': (5, 7),
            'day': (8, 10),
            'hour': (11, 13),
            'minute': (14, 16),
            'second': (17, 19),
            }
        try:
            (i, j) = table[lookup]
            return int(s[i:j])
        except:
            return None

    @staticmethod
    def web2py_regexp(expression, item):
        return re.compile(expression).search(item) is not None

    def __init__(self, db, uri, pool_size=0, folder=None, db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "sqlite"
        self.uri = uri
        self.pool_size = 0
        self.folder = folder
        self.db_codec = db_codec
        self.find_or_make_work_folder()
        path_encoding = sys.getfilesystemencoding() or locale.getdefaultlocale()[1] or 'utf8'
        if uri.startswith('sqlite:memory'):
            dbpath = ':memory:'
        else:
            dbpath = uri.split('://')[1]
            if dbpath[0] != '/':
                dbpath = os.path.join(self.folder.decode(path_encoding).encode('utf8'), dbpath)
        if not 'check_same_thread' in driver_args:
            driver_args['check_same_thread'] = False
        if not 'detect_types' in driver_args:
            driver_args['detect_types'] = self.driver.PARSE_DECLTYPES
        def connect(dbpath=dbpath, driver_args=driver_args):
            return self.driver.Connection(dbpath, **driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def after_connection(self):
        self.connection.create_function('web2py_extract', 2,
                                        SQLiteAdapter.web2py_extract)
        self.connection.create_function("REGEXP", 2,
                                        SQLiteAdapter.web2py_regexp)

    def _truncate(self, table, mode=''):
        tablename = table._tablename
        return ['DELETE FROM %s;' % tablename,
                "DELETE FROM sqlite_sequence WHERE name='%s';" % tablename]

    def lastrowid(self, table):
        return self.cursor.lastrowid

    def REGEXP(self,first,second):
        return '(%s REGEXP %s)' % (self.expand(first),
                                   self.expand(second,'string'))

    def select(self, query, fields, attributes):
        """
        Simulate SELECT ... FOR UPDATE with BEGIN IMMEDIATE TRANSACTION.
        Note that the entire database, rather than one record, is locked
        (it will be locked eventually anyway by the following UPDATE).
        """
        if attributes.get('for_update', False) and not 'cache' in attributes:
            self.execute('BEGIN IMMEDIATE TRANSACTION;')
        return super(SQLiteAdapter, self).select(query, fields, attributes)

class SpatiaLiteAdapter(SQLiteAdapter):

    import copy
    types = copy.copy(BaseAdapter.types)
    types.update({'geometry': 'GEOMETRY'})

    def __init__(self, db, uri, pool_size=0, folder=None, db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}, srid=4326):
        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "spatialite"
        self.uri = uri
        self.pool_size = 0
        self.folder = folder
        self.db_codec = db_codec
        self.find_or_make_work_folder()
        self.srid = srid
        path_encoding = sys.getfilesystemencoding() or locale.getdefaultlocale()[1] or 'utf8'
        if uri.startswith('spatialite:memory'):
            dbpath = ':memory:'
        else:
            dbpath = uri.split('://')[1]
            if dbpath[0] != '/':
                dbpath = os.path.join(self.folder.decode(path_encoding).encode('utf8'), dbpath)
        if not 'check_same_thread' in driver_args:
            driver_args['check_same_thread'] = False
        if not 'detect_types' in driver_args:
            driver_args['detect_types'] = self.driver.PARSE_DECLTYPES
        def connect(dbpath=dbpath, driver_args=driver_args):
            return self.driver.Connection(dbpath, **driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def after_connection(self):
        self.connection.enable_load_extension(True)
        # for Windows, rename libspatialite-2.dll to libspatialite.dll
        # Linux uses libspatialite.so
        # Mac OS X uses libspatialite.dylib
        libspatialite = SPATIALLIBS[platform.system()]
        self.execute(r'SELECT load_extension("%s");') % libspatialite

        self.connection.create_function('web2py_extract', 2,
                                        SQLiteAdapter.web2py_extract)
        self.connection.create_function("REGEXP", 2,
                                        SQLiteAdapter.web2py_regexp)

    # GIS functions

    def ST_ASGEOJSON(self, first, second):
        return 'AsGeoJSON(%s,%s,%s)' %(self.expand(first),
            second['precision'], second['options'])

    def ST_ASTEXT(self, first):
        return 'AsText(%s)' %(self.expand(first))

    def ST_CONTAINS(self, first, second):
        return 'Contains(%s,%s)' %(self.expand(first), self.expand(second, first.type))

    def ST_DISTANCE(self, first, second):
        return 'Distance(%s,%s)' %(self.expand(first), self.expand(second, first.type))

    def ST_EQUALS(self, first, second):
        return 'Equals(%s,%s)' %(self.expand(first), self.expand(second, first.type))

    def ST_INTERSECTS(self, first, second):
        return 'Intersects(%s,%s)' %(self.expand(first), self.expand(second, first.type))

    def ST_OVERLAPS(self, first, second):
        return 'Overlaps(%s,%s)' %(self.expand(first), self.expand(second, first.type))

    def ST_SIMPLIFY(self, first, second):
        return 'Simplify(%s,%s)' %(self.expand(first), self.expand(second, 'double'))

    def ST_TOUCHES(self, first, second):
        return 'Touches(%s,%s)' %(self.expand(first), self.expand(second, first.type))

    def ST_WITHIN(self, first, second):
        return 'Within(%s,%s)' %(self.expand(first), self.expand(second, first.type))

    def represent(self, obj, fieldtype):
        if fieldtype.startswith('geo'):
            srid = 4326 # Spatialite default srid for geometry
            geotype, parms = fieldtype[:-1].split('(')
            parms = parms.split(',')
            if len(parms) >= 2:
                schema, srid = parms[:2]
#             if fieldtype.startswith('geometry'):
            value = "ST_GeomFromText('%s',%s)" %(obj, srid)
#             elif fieldtype.startswith('geography'):
#                 value = "ST_GeogFromText('SRID=%s;%s')" %(srid, obj)
#             else:
#                 raise SyntaxError, 'Invalid field type %s' %fieldtype
            return value
        return BaseAdapter.represent(self, obj, fieldtype)


class JDBCSQLiteAdapter(SQLiteAdapter):

    driver = globals().get('zxJDBC', None)

    def __init__(self, db, uri, pool_size=0, folder=None, db_codec='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "sqlite"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.find_or_make_work_folder()
        path_encoding = sys.getfilesystemencoding() or locale.getdefaultlocale()[1] or 'utf8'
        if uri.startswith('sqlite:memory'):
            dbpath = ':memory:'
        else:
            dbpath = uri.split('://')[1]
            if dbpath[0] != '/':
                dbpath = os.path.join(self.folder.decode(path_encoding).encode('utf8'), dbpath)
        def connect(dbpath=dbpath,driver_args=driver_args):
            return self.driver.connect(java.sql.DriverManager.getConnection('jdbc:sqlite:'+dbpath), **driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def after_connection(self):
        # FIXME http://www.zentus.com/sqlitejdbc/custom_functions.html for UDFs
        self.connection.create_function('web2py_extract', 2, SQLiteAdapter.web2py_extract)

    def execute(self, a):
        return self.log_execute(a)


class MySQLAdapter(BaseAdapter):

    driver = globals().get('pymysql',None)
    maxcharlength = 255
    commit_on_alter_table = True
    support_distributed_transaction = True
    types = {
        'boolean': 'CHAR(1)',
        'string': 'VARCHAR(%(length)s)',
        'text': 'LONGTEXT',
        'password': 'VARCHAR(%(length)s)',
        'blob': 'LONGBLOB',
        'upload': 'VARCHAR(%(length)s)',
        'integer': 'INT',
        'bigint': 'BIGINT',
        'float': 'FLOAT',
        'double': 'DOUBLE',
        'decimal': 'NUMERIC(%(precision)s,%(scale)s)',
        'date': 'DATE',
        'time': 'TIME',
        'datetime': 'DATETIME',
        'id': 'INT AUTO_INCREMENT NOT NULL',
        'reference': 'INT, INDEX %(index_name)s (%(field_name)s), FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'list:integer': 'LONGTEXT',
        'list:string': 'LONGTEXT',
        'list:reference': 'LONGTEXT',
        'big-id': 'BIGINT AUTO_INCREMENT NOT NULL',
        'big-reference': 'BIGINT, INDEX %(index_name`)s (%(field_name)s), FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        }

    def varquote(self,name):
        return varquote_aux(name,'`%s`')

    def RANDOM(self):
        return 'RAND()'

    def SUBSTRING(self,field,parameters):
        return 'SUBSTRING(%s,%s,%s)' % (self.expand(field), parameters[0], parameters[1])

    def _drop(self,table,mode):
        # breaks db integrity but without this mysql does not drop table
        return ['SET FOREIGN_KEY_CHECKS=0;','DROP TABLE %s;' % table,'SET FOREIGN_KEY_CHECKS=1;']

    def distributed_transaction_begin(self,key):
        self.execute('XA START;')

    def prepare(self,key):
        self.execute("XA END;")
        self.execute("XA PREPARE;")

    def commit_prepared(self,ley):
        self.execute("XA COMMIT;")

    def rollback_prepared(self,key):
        self.execute("XA ROLLBACK;")

    def concat_add(self,table):
        return '; ALTER TABLE %s ADD ' % table

    def __init__(self,db,uri,pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "mysql"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.find_or_make_work_folder()
        uri = uri.split('://')[1]
        m = re.compile('^(?P<user>[^:@]+)(\:(?P<password>[^@]*))?@(?P<host>[^\:/]+)(\:(?P<port>[0-9]+))?/(?P<db>[^?]+)(\?set_encoding=(?P<charset>\w+))?$').match(uri)
        if not m:
            raise SyntaxError, \
                "Invalid URI string in DAL: %s" % self.uri
        user = credential_decoder(m.group('user'))
        if not user:
            raise SyntaxError, 'User required'
        password = credential_decoder(m.group('password'))
        if not password:
            password = ''
        host = m.group('host')
        if not host:
            raise SyntaxError, 'Host name required'
        db = m.group('db')
        if not db:
            raise SyntaxError, 'Database name required'
        port = int(m.group('port') or '3306')
        charset = m.group('charset') or 'utf8'
        driver_args.update(dict(db=db,
                                user=credential_decoder(user),
                                passwd=credential_decoder(password),
                                host=host,
                                port=port,
                                charset=charset))
        def connect(driver_args=driver_args):
            return self.driver.connect(**driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def after_connection(self):
        self.execute('SET FOREIGN_KEY_CHECKS=1;')
        self.execute("SET sql_mode='NO_BACKSLASH_ESCAPES';")

    def lastrowid(self,table):
        self.execute('select last_insert_id();')
        return int(self.cursor.fetchone()[0])

class PostgreSQLAdapter(BaseAdapter):

    driver = None
    drivers = {'psycopg2': globals().get('psycopg2', None),
               'pg8000': globals().get('pg8000', None), }

    support_distributed_transaction = True
    types = {
        'boolean': 'CHAR(1)',
        'string': 'VARCHAR(%(length)s)',
        'text': 'TEXT',
        'password': 'VARCHAR(%(length)s)',
        'blob': 'BYTEA',
        'upload': 'VARCHAR(%(length)s)',
        'integer': 'INTEGER',
        'bigint': 'BIGINT',
        'float': 'FLOAT',
        'double': 'FLOAT8',
        'decimal': 'NUMERIC(%(precision)s,%(scale)s)',
        'date': 'DATE',
        'time': 'TIME',
        'datetime': 'TIMESTAMP',
        'id': 'SERIAL PRIMARY KEY',
        'reference': 'INTEGER REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'list:integer': 'TEXT',
        'list:string': 'TEXT',
        'list:reference': 'TEXT',
        'geometry': 'GEOMETRY',
        'geography': 'GEOGRAPHY',
        'big-id': 'BIGSERIAL PRIMARY KEY',
        'big-reference': 'BIGINT REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        }

    def varquote(self,name):
        return varquote_aux(name,'"%s"')

    def adapt(self,obj):
        #if self.driver == self.drivers.get('pg8000'):
        #    obj = str(obj).replace('%','%%')            
        return psycopg2_adapt(obj).getquoted()

    def sequence_name(self,table):
        return '%s_id_Seq' % table

    def RANDOM(self):
        return 'RANDOM()'

    def ADD(self, first, second):
        t = first.type
        if t in ('text','string','password','upload','blob'):
            return '(%s || %s)' % (self.expand(first), self.expand(second, t))
        else:
            return '(%s + %s)' % (self.expand(first), self.expand(second, t))

    def distributed_transaction_begin(self,key):
        return

    def prepare(self,key):
        self.execute("PREPARE TRANSACTION '%s';" % key)

    def commit_prepared(self,key):
        self.execute("COMMIT PREPARED '%s';" % key)

    def rollback_prepared(self,key):
        self.execute("ROLLBACK PREPARED '%s';" % key)

    def create_sequence_and_triggers(self, query, table, **args):
        # following lines should only be executed if table._sequence_name does not exist
        # self.execute('CREATE SEQUENCE %s;' % table._sequence_name)
        # self.execute("ALTER TABLE %s ALTER COLUMN %s SET DEFAULT NEXTVAL('%s');" \
        #              % (table._tablename, table._fieldname, table._sequence_name))
        self.execute(query)

    def __init__(self,db,uri,pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}, srid=4326):
        if not self.drivers.get('psycopg2') and not self.drivers.get('pg8000'):
            raise RuntimeError, "Unable to import any drivers (psycopg2 or pg8000)"
        self.db = db
        self.dbengine = "postgres"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.srid = srid
        self.find_or_make_work_folder()
        library, uri = uri.split('://')[:2]
        m = re.compile('^(?P<user>[^:@]+)(\:(?P<password>[^@]*))?@(?P<host>[^\:@]+)(\:(?P<port>[0-9]+))?/(?P<db>[^\?]+)(\?sslmode=(?P<sslmode>.+))?$').match(uri)
        if not m:
            raise SyntaxError, "Invalid URI string in DAL"
        user = credential_decoder(m.group('user'))
        if not user:
            raise SyntaxError, 'User required'
        password = credential_decoder(m.group('password'))
        if not password:
            password = ''
        host = m.group('host')
        if not host:
            raise SyntaxError, 'Host name required'
        db = m.group('db')
        if not db:
            raise SyntaxError, 'Database name required'
        port = m.group('port') or '5432'
        sslmode = m.group('sslmode')
        if sslmode:
            msg = ("dbname='%s' user='%s' host='%s' "
                   "port=%s password='%s' sslmode='%s'") \
                   % (db, user, host, port, password, sslmode)
        else:
            msg = ("dbname='%s' user='%s' host='%s' "
                   "port=%s password='%s'") \
                   % (db, user, host, port, password)
        # choose diver according uri
        if library == "postgres":
            if 'psycopg2' in self.drivers:
                self.driver = self.drivers['psycopg2']
            elif 'pg8000' in self.drivers:
                self.driver = self.drivers['pg8000']
            else:
                raise RuntimeError, "No pgsql driver"
        elif library == "postgres:psycopg2":
            self.driver = self.drivers.get('psycopg2')
        elif library == "postgres:pg8000":
            self.driver = self.drivers.get('pg8000')
        if not self.driver:
            raise RuntimeError, "%s is not available" % library

        self.__version__ = "%s %s" % (self.driver.__name__, self.driver.__version__)
        def connect(msg=msg,driver_args=driver_args):
            return self.driver.connect(msg,**driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def after_connection(self):
        self.connection.set_client_encoding('UTF8')
        self.execute("SET standard_conforming_strings=on;")

    def lastrowid(self,table):
        self.execute("select currval('%s')" % table._sequence_name)
        return int(self.cursor.fetchone()[0])


    def LIKE(self,first,second):
        return '(%s LIKE %s)' % (self.expand(first),
                                 self.expand(second,'string'))

    def ILIKE(self,first,second):
        return '(%s ILIKE %s)' % (self.expand(first),
                                  self.expand(second,'string'))

    def REGEXP(self,first,second):
        return '(%s ~ %s)' % (self.expand(first),
                              self.expand(second,'string'))

    def STARTSWITH(self,first,second):
        return '(%s ILIKE %s)' % (self.expand(first),
                                  self.expand(second+'%','string'))

    def ENDSWITH(self,first,second):
        return '(%s ILIKE %s)' % (self.expand(first),
                                  self.expand('%'+second,'string'))

    def CONTAINS(self,first,second):
        if first.type in ('string','text'):
            key = '%'+str(second).replace('%','%%')+'%'
        elif first.type.startswith('list:'):
            key = '%|'+str(second).replace('|','||').replace('%','%%')+'|%'
        return '(%s ILIKE %s)' % (self.expand(first),self.expand(key,'string'))

    # GIS functions

    def ST_ASGEOJSON(self, first, second):
        """
        http://postgis.org/docs/ST_AsGeoJSON.html
        """
        return 'ST_AsGeoJSON(%s,%s,%s,%s)' %(second['version'],
            self.expand(first), second['precision'], second['options'])

    def ST_ASTEXT(self, first):
        """
        http://postgis.org/docs/ST_AsText.html
        """
        return 'ST_AsText(%s)' %(self.expand(first))

#     def ST_CONTAINED(self, first, second):
#         """
#         non-standard function based on ST_Contains with parameters reversed
#         http://postgis.org/docs/ST_Contains.html
#         """
#         return 'ST_Contains(%s,%s)' % (self.expand(second, first.type), self.expand(first))

    def ST_CONTAINS(self, first, second):
        """
        http://postgis.org/docs/ST_Contains.html
        """
        return 'ST_Contains(%s,%s)' %(self.expand(first), self.expand(second, first.type))

    def ST_DISTANCE(self, first, second):
        """
        http://postgis.org/docs/ST_Distance.html
        """
        return 'ST_Distance(%s,%s)' %(self.expand(first), self.expand(second, first.type))

    def ST_EQUALS(self, first, second):
        """
        http://postgis.org/docs/ST_Equals.html
        """
        return 'ST_Equals(%s,%s)' %(self.expand(first), self.expand(second, first.type))

    def ST_INTERSECTS(self, first, second):
        """
        http://postgis.org/docs/ST_Intersects.html
        """
        return 'ST_Intersects(%s,%s)' %(self.expand(first), self.expand(second, first.type))

    def ST_OVERLAPS(self, first, second):
        """
        http://postgis.org/docs/ST_Overlaps.html
        """
        return 'ST_Overlaps(%s,%s)' %(self.expand(first), self.expand(second, first.type))

    def ST_SIMPLIFY(self, first, second):
        """
        http://postgis.org/docs/ST_Simplify.html
        """
        return 'ST_Simplify(%s,%s)' %(self.expand(first), self.expand(second, 'double'))

    def ST_TOUCHES(self, first, second):
        """
        http://postgis.org/docs/ST_Touches.html
        """
        return 'ST_Touches(%s,%s)' %(self.expand(first), self.expand(second, first.type))

    def ST_WITHIN(self, first, second):
        """
        http://postgis.org/docs/ST_Within.html
        """
        return 'ST_Within(%s,%s)' %(self.expand(first), self.expand(second, first.type))

    def represent(self, obj, fieldtype):
        if fieldtype.startswith('geo'):
            srid = 4326 # postGIS default srid for geometry
            geotype, parms = fieldtype[:-1].split('(')
            parms = parms.split(',')
            if len(parms) >= 2:
                schema, srid = parms[:2]
            if fieldtype.startswith('geometry'):
                value = "ST_GeomFromText('%s',%s)" %(obj, srid)
            elif fieldtype.startswith('geography'):
                value = "ST_GeogFromText('SRID=%s;%s')" %(srid, obj)
#             else:
#                 raise SyntaxError, 'Invalid field type %s' %fieldtype
            return value
        return BaseAdapter.represent(self, obj, fieldtype)

class NewPostgreSQLAdapter(PostgreSQLAdapter):
    types = {
        'boolean': 'CHAR(1)',
        'string': 'VARCHAR(%(length)s)',
        'text': 'TEXT',
        'password': 'VARCHAR(%(length)s)',
        'blob': 'BYTEA',
        'upload': 'VARCHAR(%(length)s)',
        'integer': 'INTEGER',
        'bigint': 'BIGINT',
        'float': 'FLOAT',
        'double': 'FLOAT8',
        'decimal': 'NUMERIC(%(precision)s,%(scale)s)',
        'date': 'DATE',
        'time': 'TIME',
        'datetime': 'TIMESTAMP',
        'id': 'SERIAL PRIMARY KEY',
        'reference': 'INTEGER REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'list:integer': 'BIGINT[]',
        'list:string': 'TEXT[]',
        'list:reference': 'BIGINT[]',
        'geometry': 'GEOMETRY',
        'geography': 'GEOGRAPHY',
        'big-id': 'BIGSERIAL PRIMARY KEY',
        'big-reference': 'BIGINT REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        }

    def parse_list_integers(self, value, field_type):
        return value

    def parse_list_references(self, value, field_type):
        return [self.parse_reference(r, field_type[5:]) for r in value]

    def parse_list_strings(self, value, field_type):
        return value

    def represent(self, obj, fieldtype):
        if fieldtype.startswith('list:'):
            if not obj:
                obj = []
            elif not isinstance(obj, (list, tuple)):
                obj = [obj]
            if fieldtype.startswith('list:string'):
                obj = [str(item) for item in obj]
            else:
                obj = [int(item) for item in obj]        
            return 'ARRAY[%s]' % ','.join(repr(item) for item in obj)
        return BaseAdapter.represent(self, obj, fieldtype)


class JDBCPostgreSQLAdapter(PostgreSQLAdapter):

    def __init__(self,db,uri,pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "postgres"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.find_or_make_work_folder()
        uri = uri.split('://')[1]
        m = re.compile('^(?P<user>[^:@]+)(\:(?P<password>[^@]*))?@(?P<host>[^\:/]+)(\:(?P<port>[0-9]+))?/(?P<db>.+)$').match(uri)
        if not m:
            raise SyntaxError, "Invalid URI string in DAL"
        user = credential_decoder(m.group('user'))
        if not user:
            raise SyntaxError, 'User required'
        password = credential_decoder(m.group('password'))
        if not password:
            password = ''
        host = m.group('host')
        if not host:
            raise SyntaxError, 'Host name required'
        db = m.group('db')
        if not db:
            raise SyntaxError, 'Database name required'
        port = m.group('port') or '5432'
        msg = ('jdbc:postgresql://%s:%s/%s' % (host, port, db), user, password)
        def connect(msg=msg,driver_args=driver_args):
            return self.driver.connect(*msg,**driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def after_connection(self):
        self.connection.set_client_encoding('UTF8')
        self.execute('BEGIN;')
        self.execute("SET CLIENT_ENCODING TO 'UNICODE';")


class OracleAdapter(BaseAdapter):

    driver = globals().get('cx_Oracle',None)

    commit_on_alter_table = False
    types = {
        'boolean': 'CHAR(1)',
        'string': 'VARCHAR2(%(length)s)',
        'text': 'CLOB',
        'password': 'VARCHAR2(%(length)s)',
        'blob': 'CLOB',
        'upload': 'VARCHAR2(%(length)s)',
        'integer': 'INT',
        'bigint': 'NUMBER',
        'float': 'FLOAT',
        'double': 'BINARY_DOUBLE',
        'decimal': 'NUMERIC(%(precision)s,%(scale)s)',
        'date': 'DATE',
        'time': 'CHAR(8)',
        'datetime': 'DATE',
        'id': 'NUMBER PRIMARY KEY',
        'reference': 'NUMBER, CONSTRAINT %(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'list:integer': 'CLOB',
        'list:string': 'CLOB',
        'list:reference': 'CLOB',
        'big-id': 'NUMBER PRIMARY KEY',
        'big-reference': 'NUMBER, CONSTRAINT %(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference FK': ', CONSTRAINT FK_%(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference TFK': ' CONSTRAINT FK_%(foreign_table)s_PK FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_table)s (%(foreign_key)s) ON DELETE %(on_delete_action)s',
        }

    def sequence_name(self,tablename):
        return '%s_sequence' % tablename

    def trigger_name(self,tablename):
        return '%s_trigger' % tablename

    def LEFT_JOIN(self):
        return 'LEFT OUTER JOIN'

    def RANDOM(self):
        return 'dbms_random.value'

    def NOT_NULL(self,default,field_type):
        return 'DEFAULT %s NOT NULL' % self.represent(default,field_type)

    def _drop(self,table,mode):
        sequence_name = table._sequence_name
        return ['DROP TABLE %s %s;' % (table, mode), 'DROP SEQUENCE %s;' % sequence_name]

    def select_limitby(self, sql_s, sql_f, sql_t, sql_w, sql_o, limitby):
        if limitby:
            (lmin, lmax) = limitby
            if len(sql_w) > 1:
                sql_w_row = sql_w + ' AND w_row > %i' % lmin
            else:
                sql_w_row = 'WHERE w_row > %i' % lmin
            return 'SELECT %s %s FROM (SELECT w_tmp.*, ROWNUM w_row FROM (SELECT %s FROM %s%s%s) w_tmp WHERE ROWNUM<=%i) %s %s %s;' % (sql_s, sql_f, sql_f, sql_t, sql_w, sql_o, lmax, sql_t, sql_w_row, sql_o)
        return 'SELECT %s %s FROM %s%s%s;' % (sql_s, sql_f, sql_t, sql_w, sql_o)

    def constraint_name(self, tablename, fieldname):
        constraint_name = BaseAdapter.constraint_name(self, tablename, fieldname)
        if len(constraint_name)>30:
            constraint_name = '%s_%s__constraint' % (tablename[:10], fieldname[:7])
        return constraint_name

    def represent_exceptions(self, obj, fieldtype):
        if fieldtype == 'blob':
            obj = base64.b64encode(str(obj))
            return ":CLOB('%s')" % obj
        elif fieldtype == 'date':
            if isinstance(obj, (datetime.date, datetime.datetime)):
                obj = obj.isoformat()[:10]
            else:
                obj = str(obj)
            return "to_date('%s','yyyy-mm-dd')" % obj
        elif fieldtype == 'datetime':
            if isinstance(obj, datetime.datetime):
                obj = obj.isoformat()[:19].replace('T',' ')
            elif isinstance(obj, datetime.date):
                obj = obj.isoformat()[:10]+' 00:00:00'
            else:
                obj = str(obj)
            return "to_date('%s','yyyy-mm-dd hh24:mi:ss')" % obj
        return None

    def __init__(self,db,uri,pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "oracle"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.find_or_make_work_folder()
        uri = uri.split('://')[1]
        if not 'threaded' in driver_args:
            driver_args['threaded']=True
        def connect(uri=uri,driver_args=driver_args):
            return self.driver.connect(uri,**driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def after_connection(self):
        self.execute("ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';")
        self.execute("ALTER SESSION SET NLS_TIMESTAMP_FORMAT = 'YYYY-MM-DD HH24:MI:SS';")
    oracle_fix = re.compile("[^']*('[^']*'[^']*)*\:(?P<clob>CLOB\('([^']+|'')*'\))")

    def execute(self, command, args=None):
        args = args or []
        i = 1
        while True:
            m = self.oracle_fix.match(command)
            if not m:
                break
            command = command[:m.start('clob')] + str(i) + command[m.end('clob'):]
            args.append(m.group('clob')[6:-2].replace("''", "'"))
            i += 1
        if command[-1:]==';':
            command = command[:-1]
        return self.log_execute(command, args)

    def create_sequence_and_triggers(self, query, table, **args):
        tablename = table._tablename
        sequence_name = table._sequence_name
        trigger_name = table._trigger_name
        self.execute(query)
        self.execute('CREATE SEQUENCE %s START WITH 1 INCREMENT BY 1 NOMAXVALUE;' % sequence_name)
        self.execute('CREATE OR REPLACE TRIGGER %s BEFORE INSERT ON %s FOR EACH ROW BEGIN SELECT %s.nextval INTO :NEW.id FROM DUAL; END;\n' % (trigger_name, tablename, sequence_name))

    def lastrowid(self,table):
        sequence_name = table._sequence_name
        self.execute('SELECT %s.currval FROM dual;' % sequence_name)
        return int(self.cursor.fetchone()[0])


class MSSQLAdapter(BaseAdapter):

    driver = globals().get('pyodbc',None)

    types = {
        'boolean': 'BIT',
        'string': 'VARCHAR(%(length)s)',
        'text': 'TEXT',
        'password': 'VARCHAR(%(length)s)',
        'blob': 'IMAGE',
        'upload': 'VARCHAR(%(length)s)',
        'integer': 'INT',
        'bigint': 'BIGINT',
        'float': 'FLOAT',
        'double': 'FLOAT',
        'decimal': 'NUMERIC(%(precision)s,%(scale)s)',
        'date': 'DATETIME',
        'time': 'CHAR(8)',
        'datetime': 'DATETIME',
        'id': 'INT IDENTITY PRIMARY KEY',
        'reference': 'INT NULL, CONSTRAINT %(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'list:integer': 'TEXT',
        'list:string': 'TEXT',
        'list:reference': 'TEXT',
        'geometry': 'geometry',
        'geography': 'geography',
        'big-id': 'BIGINT IDENTITY PRIMARY KEY',
        'big-reference': 'BIGINT NULL, CONSTRAINT %(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference FK': ', CONSTRAINT FK_%(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference TFK': ' CONSTRAINT FK_%(foreign_table)s_PK FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_table)s (%(foreign_key)s) ON DELETE %(on_delete_action)s',
        }

    def varquote(self,name):
        return varquote_aux(name,'[%s]')

    def EXTRACT(self,field,what):
        return "DATEPART(%s,%s)" % (what, self.expand(field))

    def LEFT_JOIN(self):
        return 'LEFT OUTER JOIN'

    def RANDOM(self):
        return 'NEWID()'

    def ALLOW_NULL(self):
        return ' NULL'

    def SUBSTRING(self,field,parameters):
        return 'SUBSTRING(%s,%s,%s)' % (self.expand(field), parameters[0], parameters[1])

    def PRIMARY_KEY(self,key):
        return 'PRIMARY KEY CLUSTERED (%s)' % key

    def AGGREGATE(self, first, what):
        if what == 'LENGTH':
            what = 'LEN'
        return "%s(%s)" % (what, self.expand(first))

    def select_limitby(self, sql_s, sql_f, sql_t, sql_w, sql_o, limitby):
        if limitby:
            (lmin, lmax) = limitby
            sql_s += ' TOP %i' % lmax
        return 'SELECT %s %s FROM %s%s%s;' % (sql_s, sql_f, sql_t, sql_w, sql_o)

    def represent_exceptions(self, obj, fieldtype):
        if fieldtype == 'boolean':
            if obj and not str(obj)[0].upper() == 'F':
                return '1'
            else:
                return '0'
        return None

    def __init__(self,db,uri,pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                    adapter_args={}, fake_connect=False, srid=4326):
        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "mssql"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.srid = srid
        self.find_or_make_work_folder()
        # ## read: http://bytes.com/groups/python/460325-cx_oracle-utf8
        uri = uri.split('://')[1]
        if '@' not in uri:
            try:
                m = re.compile('^(?P<dsn>.+)$').match(uri)
                if not m:
                    raise SyntaxError, \
                        'Parsing uri string(%s) has no result' % self.uri
                dsn = m.group('dsn')
                if not dsn:
                    raise SyntaxError, 'DSN required'
            except SyntaxError, e:
                logger.error('NdGpatch error')
                raise e
            # was cnxn = 'DSN=%s' % dsn
            cnxn = dsn
        else:
            m = re.compile('^(?P<user>[^:@]+)(\:(?P<password>[^@]*))?@(?P<host>[^\:/]+)(\:(?P<port>[0-9]+))?/(?P<db>[^\?]+)(\?(?P<urlargs>.*))?$').match(uri)
            if not m:
                raise SyntaxError, \
                    "Invalid URI string in DAL: %s" % uri
            user = credential_decoder(m.group('user'))
            if not user:
                raise SyntaxError, 'User required'
            password = credential_decoder(m.group('password'))
            if not password:
                password = ''
            host = m.group('host')
            if not host:
                raise SyntaxError, 'Host name required'
            db = m.group('db')
            if not db:
                raise SyntaxError, 'Database name required'
            port = m.group('port') or '1433'
            # Parse the optional url name-value arg pairs after the '?'
            # (in the form of arg1=value1&arg2=value2&...)
            # Default values (drivers like FreeTDS insist on uppercase parameter keys)
            argsdict = { 'DRIVER':'{SQL Server}' }
            urlargs = m.group('urlargs') or ''
            argpattern = re.compile('(?P<argkey>[^=]+)=(?P<argvalue>[^&]*)')
            for argmatch in argpattern.finditer(urlargs):
                argsdict[str(argmatch.group('argkey')).upper()] = argmatch.group('argvalue')
            urlargs = ';'.join(['%s=%s' % (ak, av) for (ak, av) in argsdict.items()])
            cnxn = 'SERVER=%s;PORT=%s;DATABASE=%s;UID=%s;PWD=%s;%s' \
                % (host, port, db, user, password, urlargs)
        def connect(cnxn=cnxn,driver_args=driver_args):
            return self.driver.connect(cnxn,**driver_args)
        if not fake_connect:
            self.pool_connection(connect)
            self.after_connection()

    def lastrowid(self,table):
        #self.execute('SELECT @@IDENTITY;')
        self.execute('SELECT SCOPE_IDENTITY();')
        return int(self.cursor.fetchone()[0])

    def integrity_error_class(self):
        return pyodbc.IntegrityError

    def rowslice(self,rows,minimum=0,maximum=None):
        if maximum is None:
            return rows[minimum:]
        return rows[minimum:maximum]

    # GIS functions

    # No STAsGeoJSON in MSSQL

    def ST_ASTEXT(self, first):
        return '%s.STAsText()' %(self.expand(first))

    def ST_CONTAINS(self, first, second):
        return '%s.STContains(%s)=1' %(self.expand(first), self.expand(second, first.type))

    def ST_DISTANCE(self, first, second):
        return '%s.STDistance(%s)' %(self.expand(first), self.expand(second, first.type))

    def ST_EQUALS(self, first, second):
        return '%s.STEquals(%s)=1' %(self.expand(first), self.expand(second, first.type))

    def ST_INTERSECTS(self, first, second):
        return '%s.STIntersects(%s)=1' %(self.expand(first), self.expand(second, first.type))

    def ST_OVERLAPS(self, first, second):
        return '%s.STOverlaps(%s)=1' %(self.expand(first), self.expand(second, first.type))

    # no STSimplify in MSSQL

    def ST_TOUCHES(self, first, second):
        return '%s.STTouches(%s)=1' %(self.expand(first), self.expand(second, first.type))

    def ST_WITHIN(self, first, second):
        return '%s.STWithin(%s)=1' %(self.expand(first), self.expand(second, first.type))

    def represent(self, obj, fieldtype):
        if fieldtype.startswith('geometry'):
            srid = 0 # MS SQL default srid for geometry
            geotype, parms = fieldtype[:-1].split('(')
            if parms:
                srid = parms
            return "geometry::STGeomFromText('%s',%s)" %(obj, srid)
        elif fieldtype == 'geography':
            srid = 4326 # MS SQL default srid for geography
            geotype, parms = fieldtype[:-1].split('(')
            if parms:
                srid = parms
            return "geography::STGeomFromText('%s',%s)" %(obj, srid)
#             else:
#                 raise SyntaxError, 'Invalid field type %s' %fieldtype
            return "geometry::STGeomFromText('%s',%s)" %(obj, srid)
        return BaseAdapter.represent(self, obj, fieldtype)


class MSSQL2Adapter(MSSQLAdapter):
    types = {
        'boolean': 'CHAR(1)',
        'string': 'NVARCHAR(%(length)s)',
        'text': 'NTEXT',
        'password': 'NVARCHAR(%(length)s)',
        'blob': 'IMAGE',
        'upload': 'NVARCHAR(%(length)s)',
        'integer': 'INT',
        'bigint': 'BIGINT',
        'float': 'FLOAT',
        'double': 'FLOAT',
        'decimal': 'NUMERIC(%(precision)s,%(scale)s)',
        'date': 'DATETIME',
        'time': 'CHAR(8)',
        'datetime': 'DATETIME',
        'id': 'INT IDENTITY PRIMARY KEY',
        'reference': 'INT, CONSTRAINT %(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'list:integer': 'NTEXT',
        'list:string': 'NTEXT',
        'list:reference': 'NTEXT',
        'big-id': 'BIGINT IDENTITY PRIMARY KEY',
        'big-reference': 'BIGINT, CONSTRAINT %(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference FK': ', CONSTRAINT FK_%(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference TFK': ' CONSTRAINT FK_%(foreign_table)s_PK FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_table)s (%(foreign_key)s) ON DELETE %(on_delete_action)s',
        }

    def represent(self, obj, fieldtype):
        value = BaseAdapter.represent(self, obj, fieldtype)
        if (fieldtype == 'string' or fieldtype == 'text') and value[:1]=="'":
            value = 'N'+value
        return value

    def execute(self,a):
        return self.log_execute(a.decode('utf8'))

class SybaseAdapter(MSSQLAdapter):

    driver = globals().get('Sybase',None)

    types = {
        'boolean': 'BIT',
        'string': 'CHAR VARYING(%(length)s)',
        'text': 'TEXT',
        'password': 'CHAR VARYING(%(length)s)',
        'blob': 'IMAGE',
        'upload': 'CHAR VARYING(%(length)s)',
        'integer': 'INT',
        'bigint': 'BIGINT',
        'float': 'FLOAT',
        'double': 'FLOAT',
        'decimal': 'NUMERIC(%(precision)s,%(scale)s)',
        'date': 'DATETIME',
        'time': 'CHAR(8)',
        'datetime': 'DATETIME',
        'id': 'INT IDENTITY PRIMARY KEY',
        'reference': 'INT NULL, CONSTRAINT %(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'list:integer': 'TEXT',
        'list:string': 'TEXT',
        'list:reference': 'TEXT',
        'geometry': 'geometry',
        'geography': 'geography',
        'big-id': 'BIGINT IDENTITY PRIMARY KEY',
        'big-reference': 'BIGINT NULL, CONSTRAINT %(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference FK': ', CONSTRAINT FK_%(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference TFK': ' CONSTRAINT FK_%(foreign_table)s_PK FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_table)s (%(foreign_key)s) ON DELETE %(on_delete_action)s',
        }


    def __init__(self,db,uri,pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                    adapter_args={}, fake_connect=False, srid=4326):
        ### Fix this for sybase
        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "sybase"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.srid = srid
        self.find_or_make_work_folder()
        # ## read: http://bytes.com/groups/python/460325-cx_oracle-utf8
        uri = uri.split('://')[1]
        if '@' not in uri:
            try:
                m = re.compile('^(?P<dsn>.+)$').match(uri)
                if not m:
                    raise SyntaxError, \
                        'Parsing uri string(%s) has no result' % self.uri
                dsn = m.group('dsn')
                if not dsn:
                    raise SyntaxError, 'DSN required'
            except SyntaxError, e:
                logger.error('NdGpatch error')
                raise e
        else:
            m = re.compile('^(?P<user>[^:@]+)(\:(?P<password>[^@]*))?@(?P<host>[^\:/]+)(\:(?P<port>[0-9]+))?/(?P<db>[^\?]+)(\?(?P<urlargs>.*))?$').match(uri)
            if not m:
                raise SyntaxError, \
                    "Invalid URI string in DAL: %s" % uri
            user = credential_decoder(m.group('user'))
            if not user:
                raise SyntaxError, 'User required'
            password = credential_decoder(m.group('password'))
            if not password:
                password = ''
            host = m.group('host')
            if not host:
                raise SyntaxError, 'Host name required'
            db = m.group('db')
            if not db:
                raise SyntaxError, 'Database name required'
            port = m.group('port') or '1433'

            dsn = 'sybase:host=%s:%s;dbname=%s' % (host,port,db)

            driver_args.update(dict(user = credential_decoder(user),
                                    password = credential_decoder(password),
                                    locale = charset))

        def connect(dsn=dsn,driver_args=driver_args):
            return self.driver.connect(dsn,**driver_args)
        if not fake_connect:
            self.pool_connection(connect)
            self.after_connection()

    def integrity_error_class(self):
        return RuntimeError # FIX THIS


class FireBirdAdapter(BaseAdapter):

    driver = globals().get('pyodbc',None)

    commit_on_alter_table = False
    support_distributed_transaction = True
    types = {
        'boolean': 'CHAR(1)',
        'string': 'VARCHAR(%(length)s)',
        'text': 'BLOB SUB_TYPE 1',
        'password': 'VARCHAR(%(length)s)',
        'blob': 'BLOB SUB_TYPE 0',
        'upload': 'VARCHAR(%(length)s)',
        'integer': 'INTEGER',
        'bigint': 'BIGINT',
        'float': 'FLOAT',
        'double': 'DOUBLE PRECISION',
        'decimal': 'DECIMAL(%(precision)s,%(scale)s)',
        'date': 'DATE',
        'time': 'TIME',
        'datetime': 'TIMESTAMP',
        'id': 'INTEGER PRIMARY KEY',
        'reference': 'INTEGER REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'list:integer': 'BLOB SUB_TYPE 1',
        'list:string': 'BLOB SUB_TYPE 1',
        'list:reference': 'BLOB SUB_TYPE 1',
        'big-id': 'BIGINT PRIMARY KEY',
        'big-reference': 'BIGINT REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        }

    def sequence_name(self,tablename):
        return 'genid_%s' % tablename

    def trigger_name(self,tablename):
        return 'trg_id_%s' % tablename

    def RANDOM(self):
        return 'RAND()'

    def NOT_NULL(self,default,field_type):
        return 'DEFAULT %s NOT NULL' % self.represent(default,field_type)

    def SUBSTRING(self,field,parameters):
        return 'SUBSTRING(%s from %s for %s)' % (self.expand(field), parameters[0], parameters[1])

    def _drop(self,table,mode):
        sequence_name = table._sequence_name
        return ['DROP TABLE %s %s;' % (table, mode), 'DROP GENERATOR %s;' % sequence_name]

    def select_limitby(self, sql_s, sql_f, sql_t, sql_w, sql_o, limitby):
        if limitby:
            (lmin, lmax) = limitby
            sql_s += ' FIRST %i SKIP %i' % (lmax - lmin, lmin)
        return 'SELECT %s %s FROM %s%s%s;' % (sql_s, sql_f, sql_t, sql_w, sql_o)

    def _truncate(self,table,mode = ''):
        return ['DELETE FROM %s;' % table._tablename,
                'SET GENERATOR %s TO 0;' % table._sequence_name]

    def __init__(self,db,uri,pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        if adapter_args.has_key('driver_name'):
            if adapter_args['driver_name'] == 'kinterbasdb':
                self.driver = kinterbasdb
            elif adapter_args['driver_name'] == 'firebirdsql':
                self.driver = firebirdsql
        else:
            self.driver = kinterbasdb

        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "firebird"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.find_or_make_work_folder()
        uri = uri.split('://')[1]
        m = re.compile('^(?P<user>[^:@]+)(\:(?P<password>[^@]*))?@(?P<host>[^\:/]+)(\:(?P<port>[0-9]+))?/(?P<db>.+?)(\?set_encoding=(?P<charset>\w+))?$').match(uri)
        if not m:
            raise SyntaxError, "Invalid URI string in DAL: %s" % uri
        user = credential_decoder(m.group('user'))
        if not user:
            raise SyntaxError, 'User required'
        password = credential_decoder(m.group('password'))
        if not password:
            password = ''
        host = m.group('host')
        if not host:
            raise SyntaxError, 'Host name required'
        port = int(m.group('port') or 3050)
        db = m.group('db')
        if not db:
            raise SyntaxError, 'Database name required'
        charset = m.group('charset') or 'UTF8'
        driver_args.update(dict(dsn='%s/%s:%s' % (host,port,db),
                                   user = credential_decoder(user),
                                   password = credential_decoder(password),
                                   charset = charset))

        def connect(driver_args=driver_args):
            return self.driver.connect(**driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def create_sequence_and_triggers(self, query, table, **args):
        tablename = table._tablename
        sequence_name = table._sequence_name
        trigger_name = table._trigger_name
        self.execute(query)
        self.execute('create generator %s;' % sequence_name)
        self.execute('set generator %s to 0;' % sequence_name)
        self.execute('create trigger %s for %s active before insert position 0 as\nbegin\nif(new.id is null) then\nbegin\nnew.id = gen_id(%s, 1);\nend\nend;' % (trigger_name, tablename, sequence_name))

    def lastrowid(self,table):
        sequence_name = table._sequence_name
        self.execute('SELECT gen_id(%s, 0) FROM rdb$database' % sequence_name)
        return int(self.cursor.fetchone()[0])


class FireBirdEmbeddedAdapter(FireBirdAdapter):

    def __init__(self,db,uri,pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):

        if adapter_args.has_key('driver_name'):
            if adapter_args['driver_name'] == 'kinterbasdb':
                self.driver = kinterbasdb
            elif adapter_args['driver_name'] == 'firebirdsql':
                self.driver = firebirdsql
        else:
            self.driver = kinterbasdb

        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "firebird"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.find_or_make_work_folder()
        uri = uri.split('://')[1]
        m = re.compile('^(?P<user>[^:@]+)(\:(?P<password>[^@]*))?@(?P<path>[^\?]+)(\?set_encoding=(?P<charset>\w+))?$').match(uri)
        if not m:
            raise SyntaxError, \
                "Invalid URI string in DAL: %s" % self.uri
        user = credential_decoder(m.group('user'))
        if not user:
            raise SyntaxError, 'User required'
        password = credential_decoder(m.group('password'))
        if not password:
            password = ''
        pathdb = m.group('path')
        if not pathdb:
            raise SyntaxError, 'Path required'
        charset = m.group('charset')
        if not charset:
            charset = 'UTF8'
        host = ''
        driver_args.update(dict(host=host,
                                   database=pathdb,
                                   user=credential_decoder(user),
                                   password=credential_decoder(password),
                                   charset=charset))
        #def connect(driver_args=driver_args):
        #    return kinterbasdb.connect(**driver_args)

        def connect(driver_args=driver_args):
            return self.driver.connect(**driver_args)
        self.pool_connection(connect)
        self.after_connection()


class InformixAdapter(BaseAdapter):

    driver = globals().get('informixdb',None)

    types = {
        'boolean': 'CHAR(1)',
        'string': 'VARCHAR(%(length)s)',
        'text': 'BLOB SUB_TYPE 1',
        'password': 'VARCHAR(%(length)s)',
        'blob': 'BLOB SUB_TYPE 0',
        'upload': 'VARCHAR(%(length)s)',
        'integer': 'INTEGER',
        'bigint': 'BIGINT',
        'float': 'FLOAT',
        'double': 'DOUBLE PRECISION',
        'decimal': 'NUMERIC(%(precision)s,%(scale)s)',
        'date': 'DATE',
        'time': 'CHAR(8)',
        'datetime': 'DATETIME',
        'id': 'SERIAL',
        'reference': 'INTEGER REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'list:integer': 'BLOB SUB_TYPE 1',
        'list:string': 'BLOB SUB_TYPE 1',
        'list:reference': 'BLOB SUB_TYPE 1',
        'big-id': 'BIGSERIAL',
        'big-reference': 'BIGINT REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference FK': 'REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s CONSTRAINT FK_%(table_name)s_%(field_name)s',
        'reference TFK': 'FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_table)s (%(foreign_key)s) ON DELETE %(on_delete_action)s CONSTRAINT TFK_%(table_name)s_%(field_name)s',
        }

    def RANDOM(self):
        return 'Random()'

    def NOT_NULL(self,default,field_type):
        return 'DEFAULT %s NOT NULL' % self.represent(default,field_type)

    def select_limitby(self, sql_s, sql_f, sql_t, sql_w, sql_o, limitby):
        if limitby:
            (lmin, lmax) = limitby
            fetch_amt = lmax - lmin
            dbms_version = int(self.connection.dbms_version.split('.')[0])
            if lmin and (dbms_version >= 10):
                # Requires Informix 10.0+
                sql_s += ' SKIP %d' % (lmin, )
            if fetch_amt and (dbms_version >= 9):
                # Requires Informix 9.0+
                sql_s += ' FIRST %d' % (fetch_amt, )
        return 'SELECT %s %s FROM %s%s%s;' % (sql_s, sql_f, sql_t, sql_w, sql_o)

    def represent_exceptions(self, obj, fieldtype):
        if fieldtype == 'date':
            if isinstance(obj, (datetime.date, datetime.datetime)):
                obj = obj.isoformat()[:10]
            else:
                obj = str(obj)
            return "to_date('%s','%%Y-%%m-%%d')" % obj
        elif fieldtype == 'datetime':
            if isinstance(obj, datetime.datetime):
                obj = obj.isoformat()[:19].replace('T',' ')
            elif isinstance(obj, datetime.date):
                obj = obj.isoformat()[:10]+' 00:00:00'
            else:
                obj = str(obj)
            return "to_date('%s','%%Y-%%m-%%d %%H:%%M:%%S')" % obj
        return None

    def __init__(self,db,uri,pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "informix"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.find_or_make_work_folder()
        uri = uri.split('://')[1]
        m = re.compile('^(?P<user>[^:@]+)(\:(?P<password>[^@]*))?@(?P<host>[^\:/]+)(\:(?P<port>[0-9]+))?/(?P<db>.+)$').match(uri)
        if not m:
            raise SyntaxError, \
                "Invalid URI string in DAL: %s" % self.uri
        user = credential_decoder(m.group('user'))
        if not user:
            raise SyntaxError, 'User required'
        password = credential_decoder(m.group('password'))
        if not password:
            password = ''
        host = m.group('host')
        if not host:
            raise SyntaxError, 'Host name required'
        db = m.group('db')
        if not db:
            raise SyntaxError, 'Database name required'
        user = credential_decoder(user)
        password = credential_decoder(password)
        dsn = '%s@%s' % (db,host)
        driver_args.update(dict(user=user,password=password,autocommit=True))
        def connect(dsn=dsn,driver_args=driver_args):
            return self.driver.connect(dsn,**driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def execute(self,command):
        if command[-1:]==';':
            command = command[:-1]
        return self.log_execute(command)

    def lastrowid(self,table):
        return self.cursor.sqlerrd[1]

    def integrity_error_class(self):
        return informixdb.IntegrityError


class DB2Adapter(BaseAdapter):

    driver = globals().get('pyodbc',None)

    types = {
        'boolean': 'CHAR(1)',
        'string': 'VARCHAR(%(length)s)',
        'text': 'CLOB',
        'password': 'VARCHAR(%(length)s)',
        'blob': 'BLOB',
        'upload': 'VARCHAR(%(length)s)',
        'integer': 'INT',
        'bigint': 'BIGINT',
        'float': 'REAL',
        'double': 'DOUBLE',
        'decimal': 'NUMERIC(%(precision)s,%(scale)s)',
        'date': 'DATE',
        'time': 'TIME',
        'datetime': 'TIMESTAMP',
        'id': 'INT GENERATED ALWAYS AS IDENTITY PRIMARY KEY NOT NULL',
        'reference': 'INT, FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'list:integer': 'CLOB',
        'list:string': 'CLOB',
        'list:reference': 'CLOB',
        'big-id': 'BIGINT GENERATED ALWAYS AS IDENTITY PRIMARY KEY NOT NULL',
        'big-reference': 'BIGINT, FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference FK': ', CONSTRAINT FK_%(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference TFK': ' CONSTRAINT FK_%(foreign_table)s_PK FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_table)s (%(foreign_key)s) ON DELETE %(on_delete_action)s',
        }

    def LEFT_JOIN(self):
        return 'LEFT OUTER JOIN'

    def RANDOM(self):
        return 'RAND()'

    def select_limitby(self, sql_s, sql_f, sql_t, sql_w, sql_o, limitby):
        if limitby:
            (lmin, lmax) = limitby
            sql_o += ' FETCH FIRST %i ROWS ONLY' % lmax
        return 'SELECT %s %s FROM %s%s%s;' % (sql_s, sql_f, sql_t, sql_w, sql_o)

    def represent_exceptions(self, obj, fieldtype):
        if fieldtype == 'blob':
            obj = base64.b64encode(str(obj))
            return "BLOB('%s')" % obj
        elif fieldtype == 'datetime':
            if isinstance(obj, datetime.datetime):
                obj = obj.isoformat()[:19].replace('T','-').replace(':','.')
            elif isinstance(obj, datetime.date):
                obj = obj.isoformat()[:10]+'-00.00.00'
            return "'%s'" % obj
        return None

    def __init__(self,db,uri,pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "db2"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.find_or_make_work_folder()
        cnxn = uri.split('://', 1)[1]
        def connect(cnxn=cnxn,driver_args=driver_args):
            return self.driver.connect(cnxn,**driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def execute(self,command):
        if command[-1:]==';':
            command = command[:-1]
        return self.log_execute(command)

    def lastrowid(self,table):
        self.execute('SELECT DISTINCT IDENTITY_VAL_LOCAL() FROM %s;' % table)
        return int(self.cursor.fetchone()[0])

    def rowslice(self,rows,minimum=0,maximum=None):
        if maximum is None:
            return rows[minimum:]
        return rows[minimum:maximum]


class TeradataAdapter(BaseAdapter):

    driver = globals().get('pyodbc',None)

    types = {
        'boolean': 'CHAR(1)',
        'string': 'VARCHAR(%(length)s)',
        'text': 'CLOB',
        'password': 'VARCHAR(%(length)s)',
        'blob': 'BLOB',
        'upload': 'VARCHAR(%(length)s)',
        'integer': 'INT',
        'bigint': 'BIGINT',
        'float': 'REAL',
        'double': 'DOUBLE',
        'decimal': 'NUMERIC(%(precision)s,%(scale)s)',
        'date': 'DATE',
        'time': 'TIME',
        'datetime': 'TIMESTAMP',
        # Modified Constraint syntax for Teradata.
        # Teradata does not support ON DELETE.
        'id': 'INT GENERATED ALWAYS AS IDENTITY',  # Teradata Specific
        'reference': 'INT',
        'list:integer': 'CLOB',
        'list:string': 'CLOB',
        'list:reference': 'CLOB',
        'big-id': 'BIGINT GENERATED ALWAYS AS IDENTITY',  # Teradata Specific
        'big-reference': 'BIGINT',
        'reference FK': ' REFERENCES %(foreign_key)s',
        'reference TFK': ' FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_table)s (%(foreign_key)s)',
        }

    def __init__(self,db,uri,pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "teradata"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.find_or_make_work_folder()
        cnxn = uri.split('://', 1)[1]
        def connect(cnxn=cnxn,driver_args=driver_args):
            return self.driver.connect(cnxn,**driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def LEFT_JOIN(self):
        return 'LEFT OUTER JOIN'

    # Similar to MSSQL, Teradata can't specify a range (for Pageby)
    def select_limitby(self, sql_s, sql_f, sql_t, sql_w, sql_o, limitby):
        if limitby:
            (lmin, lmax) = limitby
            sql_s += ' TOP %i' % lmax
        return 'SELECT %s %s FROM %s%s%s;' % (sql_s, sql_f, sql_t, sql_w, sql_o)

    def _truncate(self, table, mode=''):
        tablename = table._tablename
        return ['DELETE FROM %s ALL;' % (tablename)]

INGRES_SEQNAME='ii***lineitemsequence' # NOTE invalid database object name
                                       # (ANSI-SQL wants this form of name
                                       # to be a delimited identifier)

class IngresAdapter(BaseAdapter):

    driver = globals().get('ingresdbi',None)

    types = {
        'boolean': 'CHAR(1)',
        'string': 'VARCHAR(%(length)s)',
        'text': 'CLOB',
        'password': 'VARCHAR(%(length)s)',  ## Not sure what this contains utf8 or nvarchar. Or even bytes?
        'blob': 'BLOB',
        'upload': 'VARCHAR(%(length)s)',  ## FIXME utf8 or nvarchar... or blob? what is this type?
        'integer': 'INTEGER4', # or int8...
        'bigint': 'BIGINT',
        'float': 'FLOAT',
        'double': 'FLOAT8',
        'decimal': 'NUMERIC(%(precision)s,%(scale)s)',
        'date': 'ANSIDATE',
        'time': 'TIME WITHOUT TIME ZONE',
        'datetime': 'TIMESTAMP WITHOUT TIME ZONE',
        'id': 'int not null unique with default next value for %s' % INGRES_SEQNAME,
        'reference': 'INT, FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'list:integer': 'CLOB',
        'list:string': 'CLOB',
        'list:reference': 'CLOB',
        'big-id': 'bigint not null unique with default next value for %s' % INGRES_SEQNAME,
        'big-reference': 'BIGINT, FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference FK': ', CONSTRAINT FK_%(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference TFK': ' CONSTRAINT FK_%(foreign_table)s_PK FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_table)s (%(foreign_key)s) ON DELETE %(on_delete_action)s', ## FIXME TODO
        }

    def LEFT_JOIN(self):
        return 'LEFT OUTER JOIN'

    def RANDOM(self):
        return 'RANDOM()'

    def select_limitby(self, sql_s, sql_f, sql_t, sql_w, sql_o, limitby):
        if limitby:
            (lmin, lmax) = limitby
            fetch_amt = lmax - lmin
            if fetch_amt:
                sql_s += ' FIRST %d ' % (fetch_amt, )
            if lmin:
                # Requires Ingres 9.2+
                sql_o += ' OFFSET %d' % (lmin, )
        return 'SELECT %s %s FROM %s%s%s;' % (sql_s, sql_f, sql_t, sql_w, sql_o)

    def __init__(self,db,uri,pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "ingres"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.find_or_make_work_folder()
        connstr = self._uri.split(':', 1)[1]
        # Simple URI processing
        connstr = connstr.lstrip()
        while connstr.startswith('/'):
            connstr = connstr[1:]
        database_name=connstr # Assume only (local) dbname is passed in
        vnode = '(local)'
        servertype = 'ingres'
        trace = (0, None) # No tracing
        driver_args.update(dict(database=database_name,
                                   vnode=vnode,
                                   servertype=servertype,
                                   trace=trace))
        def connect(driver_args=driver_args):
            return self.driver.connect(**driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def create_sequence_and_triggers(self, query, table, **args):
        # post create table auto inc code (if needed)
        # modify table to btree for performance....
        # Older Ingres releases could use rule/trigger like Oracle above.
        if hasattr(table,'_primarykey'):
            modify_tbl_sql = 'modify %s to btree unique on %s' % \
                (table._tablename,
                 ', '.join(["'%s'" % x for x in table.primarykey]))
            self.execute(modify_tbl_sql)
        else:
            tmp_seqname='%s_iisq' % table._tablename
            query=query.replace(INGRES_SEQNAME, tmp_seqname)
            self.execute('create sequence %s' % tmp_seqname)
            self.execute(query)
            self.execute('modify %s to btree unique on %s' % (table._tablename, 'id'))


    def lastrowid(self,table):
        tmp_seqname='%s_iisq' % table
        self.execute('select current value for %s' % tmp_seqname)
        return int(self.cursor.fetchone()[0]) # don't really need int type cast here...

    def integrity_error_class(self):
        return ingresdbi.IntegrityError


class IngresUnicodeAdapter(IngresAdapter):
    types = {
        'boolean': 'CHAR(1)',
        'string': 'NVARCHAR(%(length)s)',
        'text': 'NCLOB',
        'password': 'NVARCHAR(%(length)s)',  ## Not sure what this contains utf8 or nvarchar. Or even bytes?
        'blob': 'BLOB',
        'upload': 'VARCHAR(%(length)s)',  ## FIXME utf8 or nvarchar... or blob? what is this type?
        'integer': 'INTEGER4', # or int8...
        'bigint': 'BIGINT',
        'float': 'FLOAT',
        'double': 'FLOAT8',
        'decimal': 'NUMERIC(%(precision)s,%(scale)s)',
        'date': 'ANSIDATE',
        'time': 'TIME WITHOUT TIME ZONE',
        'datetime': 'TIMESTAMP WITHOUT TIME ZONE',
        'id': 'INTEGER4 not null unique with default next value for %s'% INGRES_SEQNAME,
        'reference': 'INTEGER4, FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'list:integer': 'NCLOB',
        'list:string': 'NCLOB',
        'list:reference': 'NCLOB',
        'big-id': 'BIGINT not null unique with default next value for %s'% INGRES_SEQNAME,
        'big-reference': 'BIGINT, FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference FK': ', CONSTRAINT FK_%(constraint_name)s FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'reference TFK': ' CONSTRAINT FK_%(foreign_table)s_PK FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_table)s (%(foreign_key)s) ON DELETE %(on_delete_action)s', ## FIXME TODO
        }

class SAPDBAdapter(BaseAdapter):

    driver = globals().get('sapdb',None)
    support_distributed_transaction = False
    types = {
        'boolean': 'CHAR(1)',
        'string': 'VARCHAR(%(length)s)',
        'text': 'LONG',
        'password': 'VARCHAR(%(length)s)',
        'blob': 'LONG',
        'upload': 'VARCHAR(%(length)s)',
        'integer': 'INT',
        'bigint': 'BIGINT',
        'float': 'FLOAT',
        'double': 'DOUBLE PRECISION',
        'decimal': 'FIXED(%(precision)s,%(scale)s)',
        'date': 'DATE',
        'time': 'TIME',
        'datetime': 'TIMESTAMP',
        'id': 'INT PRIMARY KEY',
        'reference': 'INT, FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        'list:integer': 'LONG',
        'list:string': 'LONG',
        'list:reference': 'LONG',
        'big-id': 'BIGINT PRIMARY KEY',
        'big-reference': 'BIGINT, FOREIGN KEY (%(field_name)s) REFERENCES %(foreign_key)s ON DELETE %(on_delete_action)s',
        }

    def sequence_name(self,table):
        return '%s_id_Seq' % table

    def select_limitby(self, sql_s, sql_f, sql_t, sql_w, sql_o, limitby):
        if limitby:
            (lmin, lmax) = limitby
            if len(sql_w) > 1:
                sql_w_row = sql_w + ' AND w_row > %i' % lmin
            else:
                sql_w_row = 'WHERE w_row > %i' % lmin
            return '%s %s FROM (SELECT w_tmp.*, ROWNO w_row FROM (SELECT %s FROM %s%s%s) w_tmp WHERE ROWNO=%i) %s %s %s;' % (sql_s, sql_f, sql_f, sql_t, sql_w, sql_o, lmax, sql_t, sql_w_row, sql_o)
        return 'SELECT %s %s FROM %s%s%s;' % (sql_s, sql_f, sql_t, sql_w, sql_o)

    def create_sequence_and_triggers(self, query, table, **args):
        # following lines should only be executed if table._sequence_name does not exist
        self.execute('CREATE SEQUENCE %s;' % table._sequence_name)
        self.execute("ALTER TABLE %s ALTER COLUMN %s SET DEFAULT NEXTVAL('%s');" \
                         % (table._tablename, table._id.name, table._sequence_name))
        self.execute(query)

    def __init__(self,db,uri,pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "sapdb"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.find_or_make_work_folder()
        uri = uri.split('://')[1]
        m = re.compile('^(?P<user>[^:@]+)(\:(?P<password>[^@]*))?@(?P<host>[^\:@]+)(\:(?P<port>[0-9]+))?/(?P<db>[^\?]+)(\?sslmode=(?P<sslmode>.+))?$').match(uri)
        if not m:
            raise SyntaxError, "Invalid URI string in DAL"
        user = credential_decoder(m.group('user'))
        if not user:
            raise SyntaxError, 'User required'
        password = credential_decoder(m.group('password'))
        if not password:
            password = ''
        host = m.group('host')
        if not host:
            raise SyntaxError, 'Host name required'
        db = m.group('db')
        if not db:
            raise SyntaxError, 'Database name required'
        def connect(user=user, password=password, database=db,
                    host=host, driver_args=driver_args):
            return self.driver.Connection(user, password, database,
                                          host, **driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def lastrowid(self,table):
        self.execute("select %s.NEXTVAL from dual" % table._sequence_name)
        return int(self.cursor.fetchone()[0])

class CubridAdapter(MySQLAdapter):

    driver = globals().get('cubriddb', None)

    def __init__(self, db, uri, pool_size=0, folder=None, db_codec='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        if not self.driver:
            raise RuntimeError, "Unable to import driver"
        self.db = db
        self.dbengine = "cubrid"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.find_or_make_work_folder()
        uri = uri.split('://')[1]
        m = re.compile('^(?P<user>[^:@]+)(\:(?P<password>[^@]*))?@(?P<host>[^\:/]+)(\:(?P<port>[0-9]+))?/(?P<db>[^?]+)(\?set_encoding=(?P<charset>\w+))?$').match(uri)
        if not m:
            raise SyntaxError, \
                "Invalid URI string in DAL: %s" % self.uri
        user = credential_decoder(m.group('user'))
        if not user:
            raise SyntaxError, 'User required'
        password = credential_decoder(m.group('password'))
        if not password:
            password = ''
        host = m.group('host')
        if not host:
            raise SyntaxError, 'Host name required'
        db = m.group('db')
        if not db:
            raise SyntaxError, 'Database name required'
        port = int(m.group('port') or '30000')
        charset = m.group('charset') or 'utf8'
        user = credential_decoder(user)
        passwd = credential_decoder(password)
        def connect(host=host,port=port,db=db,
                    user=user,passwd=password,driver_args=driver_args):
            return self.driver.connect(host,port,db,user,passwd,**driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def after_connection(self):
        self.execute('SET FOREIGN_KEY_CHECKS=1;')
        self.execute("SET sql_mode='NO_BACKSLASH_ESCAPES';")


######## GAE MySQL ##########

class DatabaseStoredFile:

    web2py_filesystem = False

    def escape(self,obj):
        return self.db._adapter.escape(obj)

    def __init__(self,db,filename,mode):
        if db._adapter.dbengine != 'mysql':
            raise RuntimeError, "only MySQL can store metadata .table files in database for now"
        self.db = db
        self.filename = filename
        self.mode = mode
        if not self.web2py_filesystem:
            self.db.executesql("CREATE TABLE IF NOT EXISTS web2py_filesystem (path VARCHAR(512), content LONGTEXT, PRIMARY KEY(path) ) ENGINE=InnoDB;")
            DatabaseStoredFile.web2py_filesystem = True
        self.p=0
        self.data = ''
        if mode in ('r','rw','a'):
            query = "SELECT content FROM web2py_filesystem WHERE path='%s'" \
                % filename
            rows = self.db.executesql(query)
            if rows:
                self.data = rows[0][0]
            elif os.path.exists(filename):
                datafile = open(filename, 'r')
                try:
                    self.data = datafile.read()
                finally:
                    datafile.close()
            elif mode in ('r','rw'):
                raise RuntimeError, "File %s does not exist" % filename

    def read(self, bytes):
        data = self.data[self.p:self.p+bytes]
        self.p += len(data)
        return data

    def readline(self):
        i = self.data.find('\n',self.p)+1
        if i>0:
            data, self.p = self.data[self.p:i], i
        else:
            data, self.p = self.data[self.p:], len(self.data)
        return data

    def write(self,data):
        self.data += data

    def close(self):
        self.db.executesql("DELETE FROM web2py_filesystem WHERE path='%s'" \
                               % self.filename)
        query = "INSERT INTO web2py_filesystem(path,content) VALUES ('%s','%s')"\
            % (self.filename, self.data.replace("'","''"))
        self.db.executesql(query)
        self.db.commit()

    @staticmethod
    def exists(db, filename):
        if os.path.exists(filename):
            return True
        query = "SELECT path FROM web2py_filesystem WHERE path='%s'" % filename
        if db.executesql(query):
            return True
        return False


class UseDatabaseStoredFile:

    def file_exists(self, filename):
        return DatabaseStoredFile.exists(self.db,filename)

    def file_open(self, filename, mode='rb', lock=True):
        return DatabaseStoredFile(self.db,filename,mode)

    def file_close(self, fileobj):
        fileobj.close()

    def file_delete(self,filename):
        query = "DELETE FROM web2py_filesystem WHERE path='%s'" % filename
        self.db.executesql(query)
        self.db.commit()

class GoogleSQLAdapter(UseDatabaseStoredFile,MySQLAdapter):
    uploads_in_blob = True

    def __init__(self, db, uri='google:sql://realm:domain/database',
                 pool_size=0, folder=None, db_codec='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):

        self.db = db
        self.dbengine = "mysql"
        self.uri = uri
        self.pool_size = pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.folder = folder or '$HOME/'+thread.folder.split('/applications/',1)[1]

        m = re.compile('^(?P<instance>.*)/(?P<db>.*)$').match(self.uri[len('google:sql://'):])
        if not m:
            raise SyntaxError, "Invalid URI string in SQLDB: %s" % self._uri
        instance = credential_decoder(m.group('instance'))
        self.dbstring = db = credential_decoder(m.group('db'))
        driver_args['instance'] = instance
        self.createdb = createdb = adapter_args.get('createdb',True)
        if not createdb:
            driver_args['database'] = db
        def connect(driver_args=driver_args):
            return rdbms.connect(**driver_args)
        self.pool_connection(connect)
        self.after_connection()

    def after_connection(self):
        if self.createdb:
            # self.execute('DROP DATABASE %s' % self.dbstring)
            self.execute('CREATE DATABASE IF NOT EXISTS %s' % self.dbstring)
            self.execute('USE %s' % self.dbstring)
        self.execute("SET FOREIGN_KEY_CHECKS=1;")
        self.execute("SET sql_mode='NO_BACKSLASH_ESCAPES';")

class NoSQLAdapter(BaseAdapter):
    can_select_for_update = False

    @staticmethod
    def to_unicode(obj):
        if isinstance(obj, str):
            return obj.decode('utf8')
        elif not isinstance(obj, unicode):
            return unicode(obj)
        return obj

    def represent(self, obj, fieldtype):
        if isinstance(obj, CALLABLETYPES):
            obj = obj()
        if isinstance(fieldtype, SQLCustomType):
            return fieldtype.encoder(obj)
        if isinstance(obj, (Expression, Field)):
            raise SyntaxError, "non supported on GAE"
        if self.dbengine == 'google:datastore':
            if isinstance(fieldtype, gae.Property):
                return obj
        is_string = isinstance(fieldtype,str)
        is_list = is_string and fieldtype.startswith('list:')
        if is_list:
            if not obj:
                obj = []
            if not isinstance(obj, (list, tuple)):
                obj = [obj]
        if obj == '' and not \
                (is_string and fieldtype[:2] in ['st','te','pa','up']):
            return None
        if not obj is None:
            if isinstance(obj, list) and not is_list:
                obj = [self.represent(o, fieldtype) for o in obj]
            elif fieldtype in ('integer','bigint','id'):
                obj = long(obj)
            elif fieldtype == 'double':
                obj = float(obj)
            elif is_string and fieldtype.startswith('reference'):
                if isinstance(obj, (Row, Reference)):
                    obj = obj['id']
                obj = long(obj)
            elif fieldtype == 'boolean':
                if obj and not str(obj)[0].upper() == 'F':
                    obj = True
                else:
                    obj = False
            elif fieldtype == 'date':
                if not isinstance(obj, datetime.date):
                    (y, m, d) = map(int,str(obj).strip().split('-'))
                    obj = datetime.date(y, m, d)
                elif isinstance(obj,datetime.datetime):
                    (y, m, d) = (obj.year, obj.month, obj.day)
                    obj = datetime.date(y, m, d)
            elif fieldtype == 'time':
                if not isinstance(obj, datetime.time):
                    time_items = map(int,str(obj).strip().split(':')[:3])
                    if len(time_items) == 3:
                        (h, mi, s) = time_items
                    else:
                        (h, mi, s) = time_items + [0]
                    obj = datetime.time(h, mi, s)
            elif fieldtype == 'datetime':
                if not isinstance(obj, datetime.datetime):
                    (y, m, d) = map(int,str(obj)[:10].strip().split('-'))
                    time_items = map(int,str(obj)[11:].strip().split(':')[:3])
                    while len(time_items)<3:
                        time_items.append(0)
                    (h, mi, s) = time_items
                    obj = datetime.datetime(y, m, d, h, mi, s)
            elif fieldtype == 'blob':
                pass
            elif is_string and fieldtype.startswith('list:string'):
                return map(self.to_unicode,obj)
            elif is_list:
                return map(int,obj)
            else:
                obj = self.to_unicode(obj)
        return obj

    def _insert(self,table,fields):
        return 'insert %s in %s' % (fields, table)

    def _count(self,query,distinct=None):
        return 'count %s' % repr(query)

    def _select(self,query,fields,attributes):
        return 'select %s where %s' % (repr(fields), repr(query))

    def _delete(self,tablename, query):
        return 'delete %s where %s' % (repr(tablename),repr(query))

    def _update(self,tablename,query,fields):
        return 'update %s (%s) where %s' % (repr(tablename),
                                            repr(fields),repr(query))

    def commit(self):
        """
        remember: no transactions on many NoSQL
        """
        pass

    def rollback(self):
        """
        remember: no transactions on many NoSQL
        """
        pass

    def close(self):
        """
        remember: no transactions on many NoSQL
        """
        pass


    # these functions should never be called!
    def OR(self,first,second): raise SyntaxError, "Not supported"
    def AND(self,first,second): raise SyntaxError, "Not supported"
    def AS(self,first,second): raise SyntaxError, "Not supported"
    def ON(self,first,second): raise SyntaxError, "Not supported"
    def STARTSWITH(self,first,second=None): raise SyntaxError, "Not supported"
    def ENDSWITH(self,first,second=None): raise SyntaxError, "Not supported"
    def ADD(self,first,second): raise SyntaxError, "Not supported"
    def SUB(self,first,second): raise SyntaxError, "Not supported"
    def MUL(self,first,second): raise SyntaxError, "Not supported"
    def DIV(self,first,second): raise SyntaxError, "Not supported"
    def LOWER(self,first): raise SyntaxError, "Not supported"
    def UPPER(self,first): raise SyntaxError, "Not supported"
    def EXTRACT(self,first,what): raise SyntaxError, "Not supported"
    def AGGREGATE(self,first,what): raise SyntaxError, "Not supported"
    def LEFT_JOIN(self): raise SyntaxError, "Not supported"
    def RANDOM(self): raise SyntaxError, "Not supported"
    def SUBSTRING(self,field,parameters):  raise SyntaxError, "Not supported"
    def PRIMARY_KEY(self,key):  raise SyntaxError, "Not supported"
    def ILIKE(self,first,second): raise SyntaxError, "Not supported"
    def drop(self,table,mode):  raise SyntaxError, "Not supported"
    def alias(self,table,alias): raise SyntaxError, "Not supported"
    def migrate_table(self,*a,**b): raise SyntaxError, "Not supported"
    def distributed_transaction_begin(self,key): raise SyntaxError, "Not supported"
    def prepare(self,key): raise SyntaxError, "Not supported"
    def commit_prepared(self,key): raise SyntaxError, "Not supported"
    def rollback_prepared(self,key): raise SyntaxError, "Not supported"
    def concat_add(self,table): raise SyntaxError, "Not supported"
    def constraint_name(self, table, fieldname): raise SyntaxError, "Not supported"
    def create_sequence_and_triggers(self, query, table, **args): pass
    def log_execute(self,*a,**b): raise SyntaxError, "Not supported"
    def execute(self,*a,**b): raise SyntaxError, "Not supported"
    def represent_exceptions(self, obj, fieldtype): raise SyntaxError, "Not supported"
    def lastrowid(self,table): raise SyntaxError, "Not supported"
    def integrity_error_class(self): raise SyntaxError, "Not supported"
    def rowslice(self,rows,minimum=0,maximum=None): raise SyntaxError, "Not supported"


class GAEF(object):
    def __init__(self,name,op,value,apply):
        self.name=name=='id' and '__key__' or name
        self.op=op
        self.value=value
        self.apply=apply
    def __repr__(self):
        return '(%s %s %s:%s)' % (self.name, self.op, repr(self.value), type(self.value))

class GoogleDatastoreAdapter(NoSQLAdapter):
    uploads_in_blob = True
    types = {}

    def file_exists(self, filename): pass
    def file_open(self, filename, mode='rb', lock=True): pass
    def file_close(self, fileobj): pass

    def __init__(self,db,uri,pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        self.types.update({
                'boolean': gae.BooleanProperty,
                'string': (lambda: gae.StringProperty(multiline=True)),
                'text': gae.TextProperty,
                'password': gae.StringProperty,
                'blob': gae.BlobProperty,
                'upload': gae.StringProperty,
                'integer': gae.IntegerProperty,
                'bigint': gae.IntegerProperty,
                'float': gae.FloatProperty,
                'double': gae.FloatProperty,
                'decimal': GAEDecimalProperty,
                'date': gae.DateProperty,
                'time': gae.TimeProperty,
                'datetime': gae.DateTimeProperty,
                'id': None,
                'reference': gae.IntegerProperty,
                'list:string': (lambda: gae.StringListProperty(default=None)),
                'list:integer': (lambda: gae.ListProperty(int,default=None)),
                'list:reference': (lambda: gae.ListProperty(int,default=None)),
        })
        self.db = db
        self.uri = uri
        self.dbengine = 'google:datastore'
        self.folder = folder
        db['_lastsql'] = ''
        self.db_codec = 'UTF-8'
        self.pool_size = 0
        match = re.compile('.*://(?P<namespace>.+)').match(uri)
        if match:
            namespace_manager.set_namespace(match.group('namespace'))

    def parse_id(self, value, field_type):
        return value
        
    def create_table(self,table,migrate=True,fake_migrate=False, polymodel=None):
        myfields = {}
        for k in table.fields:
            if isinstance(polymodel,Table) and k in polymodel.fields():
                continue
            field = table[k]
            attr = {}
            if isinstance(field.type, SQLCustomType):
                ftype = self.types[field.type.native or field.type.type](**attr)
            elif isinstance(field.type, gae.Property):
                ftype = field.type
            elif field.type.startswith('id'):
                continue
            elif field.type.startswith('decimal'):
                precision, scale = field.type[7:].strip('()').split(',')
                precision = int(precision)
                scale = int(scale)
                ftype = GAEDecimalProperty(precision, scale, **attr)
            elif field.type.startswith('reference'):
                if field.notnull:
                    attr = dict(required=True)
                referenced = field.type[10:].strip()
                ftype = self.types[field.type[:9]](referenced)
            elif field.type.startswith('list:reference'):
                if field.notnull:
                    attr = dict(required=True)
                referenced = field.type[15:].strip()
                ftype = self.types[field.type[:14]](**attr)
            elif field.type.startswith('list:'):
                ftype = self.types[field.type](**attr)
            elif not field.type in self.types\
                 or not self.types[field.type]:
                raise SyntaxError, 'Field: unknown field type: %s' % field.type
            else:
                ftype = self.types[field.type](**attr)
            myfields[field.name] = ftype
        if not polymodel:
            table._tableobj = classobj(table._tablename, (gae.Model, ), myfields)
        elif polymodel==True:
            table._tableobj = classobj(table._tablename, (PolyModel, ), myfields)
        elif isinstance(polymodel,Table):
            table._tableobj = classobj(table._tablename, (polymodel._tableobj, ), myfields)
        else:
            raise SyntaxError, "polymodel must be None, True, a table or a tablename"
        return None

    def expand(self,expression,field_type=None):
        if isinstance(expression,Field):
            if expression.type in ('text','blob'):
                raise SyntaxError, 'AppEngine does not index by: %s' % expression.type
            return expression.name
        elif isinstance(expression, (Expression, Query)):
            if not expression.second is None:
                return expression.op(expression.first, expression.second)
            elif not expression.first is None:
                return expression.op(expression.first)
            else:
                return expression.op()
        elif field_type:
                return self.represent(expression,field_type)
        elif isinstance(expression,(list,tuple)):
            return ','.join([self.represent(item,field_type) for item in expression])
        else:
            return str(expression)

    ### TODO from gql.py Expression
    def AND(self,first,second):
        a = self.expand(first)
        b = self.expand(second)
        if b[0].name=='__key__' and a[0].name!='__key__':
            return b+a
        return a+b

    def EQ(self,first,second=None):
        if isinstance(second, Key):
            return [GAEF(first.name,'=',second,lambda a,b:a==b)]
        return [GAEF(first.name,'=',self.represent(second,first.type),lambda a,b:a==b)]

    def NE(self,first,second=None):
        if first.type != 'id':
            return [GAEF(first.name,'!=',self.represent(second,first.type),lambda a,b:a!=b)]
        else:
            second = Key.from_path(first._tablename, long(second))
            return [GAEF(first.name,'!=',second,lambda a,b:a!=b)]

    def LT(self,first,second=None):
        if first.type != 'id':
            return [GAEF(first.name,'<',self.represent(second,first.type),lambda a,b:a<b)]
        else:
            second = Key.from_path(first._tablename, long(second))
            return [GAEF(first.name,'<',second,lambda a,b:a<b)]

    def LE(self,first,second=None):
        if first.type != 'id':
            return [GAEF(first.name,'<=',self.represent(second,first.type),lambda a,b:a<=b)]
        else:
            second = Key.from_path(first._tablename, long(second))
            return [GAEF(first.name,'<=',second,lambda a,b:a<=b)]

    def GT(self,first,second=None):
        if first.type != 'id' or second==0 or second == '0':
            return [GAEF(first.name,'>',self.represent(second,first.type),lambda a,b:a>b)]
        else:
            second = Key.from_path(first._tablename, long(second))
            return [GAEF(first.name,'>',second,lambda a,b:a>b)]

    def GE(self,first,second=None):
        if first.type != 'id':
            return [GAEF(first.name,'>=',self.represent(second,first.type),lambda a,b:a>=b)]
        else:
            second = Key.from_path(first._tablename, long(second))
            return [GAEF(first.name,'>=',second,lambda a,b:a>=b)]

    def INVERT(self,first):
        return '-%s' % first.name

    def COMMA(self,first,second):
        return '%s, %s' % (self.expand(first),self.expand(second))

    def BELONGS(self,first,second=None):
        if not isinstance(second,(list, tuple)):
            raise SyntaxError, "Not supported"
        if first.type != 'id':
            return [GAEF(first.name,'in',self.represent(second,first.type),lambda a,b:a in b)]
        else:
            second = [Key.from_path(first._tablename, i) for i in second]
            return [GAEF(first.name,'in',second,lambda a,b:a in b)]

    def CONTAINS(self,first,second):
        if not first.type.startswith('list:'):
            raise SyntaxError, "Not supported"
        return [GAEF(first.name,'=',self.expand(second,first.type[5:]),lambda a,b:b in a)]

    def NOT(self,first):
        nops = { self.EQ: self.NE,
                 self.NE: self.EQ,
                 self.LT: self.GE,
                 self.GT: self.LE,
                 self.LE: self.GT,
                 self.GE: self.LT}
        if not isinstance(first,Query):
            raise SyntaxError, "Not suported"
        nop = nops.get(first.op,None)
        if not nop:
            raise SyntaxError, "Not suported %s" % first.op.__name__
        first.op = nop
        return self.expand(first)

    def truncate(self,table,mode):
        self.db(table._id > 0).delete()

    def select_raw(self,query,fields=None,attributes=None):
        fields = fields or []
        attributes = attributes or {}
        new_fields = []
        for item in fields:
            if isinstance(item,SQLALL):
                new_fields += item._table
            else:
                new_fields.append(item)
        fields = new_fields
        if query:
            tablename = self.get_table(query)
        elif fields:
            tablename = fields[0].tablename
            query = fields[0].table._id>0
        else:
            raise SyntaxError, "Unable to determine a tablename"

        if query:
            if use_common_filters(query):
                query = self.common_filter(query,[tablename])

        #tableobj is a GAE Model class (or subclass)
        tableobj = self.db[tablename]._tableobj
        filters = self.expand(query)

        projection = None
        if len(self.db[tablename].fields) == len(fields):
            #getting all fields, not a projection query
            projection = None
        elif attributes.get('projection') == True:
            projection = []
            for f in fields:
                if f.type in ['text', 'blob']:
                    raise SyntaxError, \
                    "text and blob field types not allowed in projection queries"
                else:
                    projection.append(f.name)

        #projection's can't include 'id'.  it will be added to the result later
        query_projection = [p for p in projection if \
                            p != self.db[tablename]._id.name] if projection \
                            else None

        cursor = None
        if isinstance(attributes.get('reusecursor'), str):
            cursor = attributes.get('reusecursor')
        items = gae.Query(tableobj, projection=query_projection, cursor=cursor)
        
        for filter in filters:
            if attributes.get('projection') == True and \
               filter.name in query_projection and \
               filter.op in ['=', '<=', '>=']:
                raise SyntaxError, \
                "projection fields cannot have equality filters"
            if filter.name=='__key__' and filter.op=='>' and filter.value==0:
                continue
            elif filter.name=='__key__' and filter.op=='=':
                if filter.value==0:
                    items = []
                elif isinstance(filter.value, Key):
                    #key qeuries return a class instance, can't use projection
                    #  extra values will be ignored in post-processing later
                    item = tableobj.get(filter.value)
                    items = (item and [item]) or []
                else:
                    #key qeuries return a class instance, can't use projection
                    #  extra values will be ignored in post-processing later
                    item = tableobj.get_by_id(filter.value)
                    items = (item and [item]) or []
            elif isinstance(items,list): # i.e. there is a single record!
                items = [i for i in items if filter.apply(
                        getattr(item,filter.name),filter.value)]
            else:
                if filter.name=='__key__':
                    items.order('__key__')
                items = items.filter('%s %s' % (filter.name,filter.op),
                                     filter.value)
        if not isinstance(items,list):
            if attributes.get('left', None):
                raise SyntaxError, 'Set: no left join in appengine'
            if attributes.get('groupby', None):
                raise SyntaxError, 'Set: no groupby in appengine'
            orderby = attributes.get('orderby', False)
            if orderby:
                ### THIS REALLY NEEDS IMPROVEMENT !!!
                if isinstance(orderby, (list, tuple)):
                    orderby = xorify(orderby)
                if isinstance(orderby,Expression):
                    orderby = self.expand(orderby)
                orders = orderby.split(', ')
                for order in orders:
                    order={'-id':'-__key__','id':'__key__'}.get(order,order)
                    items = items.order(order)
            if attributes.get('limitby', None):
                (lmin, lmax) = attributes['limitby']
                (limit, offset) = (lmax - lmin, lmin)
                rows = items.fetch(limit,offset=offset)
                #cursor is only useful if there was a limit and we didn't return
                # all results
                if attributes.get('reusecursor'):
                    self.db['_lastcursor'] = items.cursor()
                items = rows
        return (items, tablename, projection or self.db[tablename].fields)

    def select(self,query,fields,attributes):
        """
        This is the GAE version of select.  some notes to consider:
         - db['_lastsql'] is not set because there is not SQL statement string
           for a GAE query
         - 'nativeRef' is a magical fieldname used for self references on GAE
         - optional attribute 'projection' when set to True will trigger
           use of the GAE projection queries.  note that there are rules for
           what is accepted imposed by GAE: each field must be indexed,
           projection queries cannot contain blob or text fields, and you
           cannot use == and also select that same field.  see https://developers.google.com/appengine/docs/python/datastore/queries#Query_Projection
         - optional attribute 'reusecursor' allows use of cursor with queries
           that have the limitby attribute.  Set the attribute to True for the
           first query, set it to the value of db['_lastcursor'] to continue
           a previous query.  The user must save the cursor value between
           requests, and the filters must be identical.  It is up to the user
           to follow google's limitations: https://developers.google.com/appengine/docs/python/datastore/queries#Query_Cursors
        """
        
        (items, tablename, fields) = self.select_raw(query,fields,attributes)
        # self.db['_lastsql'] = self._select(query,fields,attributes)
        rows = [[(t==self.db[tablename]._id.name and item) or \
                 (t=='nativeRef' and item) or getattr(item, t) \
                     for t in fields] for item in items]
        colnames = ['%s.%s' % (tablename, t) for t in fields]
        processor = attributes.get('processor',self.parse)
        return processor(rows,fields,colnames,False)

    def count(self,query,distinct=None):
        if distinct:
            raise RuntimeError, "COUNT DISTINCT not supported"
        (items, tablename, fields) = self.select_raw(query)
        # self.db['_lastsql'] = self._count(query)
        try:
            return len(items)
        except TypeError:
            return items.count(limit=None)

    def delete(self,tablename, query):
        """
        This function was changed on 2010-05-04 because according to
        http://code.google.com/p/googleappengine/issues/detail?id=3119
        GAE no longer supports deleting more than 1000 records.
        """
        # self.db['_lastsql'] = self._delete(tablename,query)
        (items, tablename, fields) = self.select_raw(query)
        # items can be one item or a query
        if not isinstance(items,list):
            counter = items.count(limit=None)
            leftitems = items.fetch(1000)
            while len(leftitems):
                gae.delete(leftitems)
                leftitems = items.fetch(1000)
        else:
            counter = len(items)
            gae.delete(items)
        return counter

    def update(self,tablename,query,update_fields):
        # self.db['_lastsql'] = self._update(tablename,query,update_fields)
        (items, tablename, fields) = self.select_raw(query)
        counter = 0
        for item in items:
            for field, value in update_fields:
                setattr(item, field.name, self.represent(value,field.type))
            item.put()
            counter += 1
        logger.info(str(counter))
        return counter

    def insert(self,table,fields):
        dfields=dict((f.name,self.represent(v,f.type)) for f,v in fields)
        # table._db['_lastsql'] = self._insert(table,fields)
        tmp = table._tableobj(**dfields)
        tmp.put()
        rid = Reference(tmp.key().id())
        (rid._table, rid._record, rid._gaekey) = (table, None, tmp.key())
        return rid

    def bulk_insert(self,table,items):
        parsed_items = []
        for item in items:
            dfields=dict((f.name,self.represent(v,f.type)) for f,v in item)
            parsed_items.append(table._tableobj(**dfields))
        gae.put(parsed_items)
        return True

def uuid2int(uuidv):
    return uuid.UUID(uuidv).int

def int2uuid(n):
    return str(uuid.UUID(int=n))

class CouchDBAdapter(NoSQLAdapter):
    uploads_in_blob = True
    types = {
                'boolean': bool,
                'string': str,
                'text': str,
                'password': str,
                'blob': str,
                'upload': str,
                'integer': long,
                'bigint': long,
                'float': float,
                'double': float,
                'date': datetime.date,
                'time': datetime.time,
                'datetime': datetime.datetime,
                'id': long,
                'reference': long,
                'list:string': list,
                'list:integer': list,
                'list:reference': list,
        }

    def file_exists(self, filename): pass
    def file_open(self, filename, mode='rb', lock=True): pass
    def file_close(self, fileobj): pass

    def expand(self,expression,field_type=None):
        if isinstance(expression,Field):
            if expression.type=='id':
                return "%s._id" % expression.tablename
        return BaseAdapter.expand(self,expression,field_type)

    def AND(self,first,second):
        return '(%s && %s)' % (self.expand(first),self.expand(second))

    def OR(self,first,second):
        return '(%s || %s)' % (self.expand(first),self.expand(second))

    def EQ(self,first,second):
        if second is None:
            return '(%s == null)' % self.expand(first)
        return '(%s == %s)' % (self.expand(first),self.expand(second,first.type))

    def NE(self,first,second):
        if second is None:
            return '(%s != null)' % self.expand(first)
        return '(%s != %s)' % (self.expand(first),self.expand(second,first.type))

    def COMMA(self,first,second):
        return '%s + %s' % (self.expand(first),self.expand(second))

    def represent(self, obj, fieldtype):
        value = NoSQLAdapter.represent(self, obj, fieldtype)
        if fieldtype=='id':
            return repr(str(int(value)))
        elif fieldtype in ('date','time','datetime','boolean'):
            return serializers.json(value)
        return repr(not isinstance(value,unicode) and value or value.encode('utf8'))

    def __init__(self,db,uri='couchdb://127.0.0.1:5984',
                 pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        self.db = db
        self.uri = uri
        self.dbengine = 'couchdb'
        self.folder = folder
        db['_lastsql'] = ''
        self.db_codec = 'UTF-8'
        self.pool_size = pool_size

        url='http://'+uri[10:]
        def connect(url=url,driver_args=driver_args):
            return couchdb.Server(url,**driver_args)
        self.pool_connection(connect,cursor=False)
        self.after_connection()

    def create_table(self, table, migrate=True, fake_migrate=False, polymodel=None):
        if migrate:
            try:
                self.connection.create(table._tablename)
            except:
                pass

    def insert(self,table,fields):
        id = uuid2int(web2py_uuid())
        ctable = self.connection[table._tablename]
        values = dict((k.name,self.represent(v,k.type)) for k,v in fields)
        values['_id'] = str(id)
        ctable.save(values)
        return id

    def _select(self,query,fields,attributes):
        if not isinstance(query,Query):
            raise SyntaxError, "Not Supported"
        for key in set(attributes.keys())-set(('orderby','groupby','limitby',
                                               'required','cache','left',
                                               'distinct', 'having', 'processor')):
            raise SyntaxError, 'invalid select attribute: %s' % key
        new_fields=[]
        for item in fields:
            if isinstance(item,SQLALL):
                new_fields += item._table
            else:
                new_fields.append(item)
        def uid(fd):
            return fd=='id' and '_id' or fd
        def get(row,fd):
            return fd=='id' and int(row['_id']) or row.get(fd,None)
        fields = new_fields
        tablename = self.get_table(query)
        fieldnames = [f.name for f in (fields or self.db[tablename])]
        colnames = ['%s.%s' % (tablename,k) for k in fieldnames]
        fields = ','.join(['%s.%s' % (tablename,uid(f)) for f in fieldnames])
        fn="function(%(t)s){if(%(query)s)emit(%(order)s,[%(fields)s]);}" %\
            dict(t=tablename,
                 query=self.expand(query),
                 order='%s._id' % tablename,
                 fields=fields)
        return fn, colnames

    def select(self,query,fields,attributes):
        if not isinstance(query,Query):
            raise SyntaxError, "Not Supported"
        fn, colnames = self._select(query,fields,attributes)
        tablename = colnames[0].split('.')[0]
        ctable = self.connection[tablename]
        rows = [cols['value'] for cols in ctable.query(fn)]
        processor = attributes.get('processor',self.parse)
        return processor(rows,fields,colnames,False)

    def delete(self,tablename,query):
        if not isinstance(query,Query):
            raise SyntaxError, "Not Supported"
        if query.first.type=='id' and query.op==self.EQ:
            id = query.second
            tablename = query.first.tablename
            assert(tablename == query.first.tablename)
            ctable = self.connection[tablename]
            try:
                del ctable[str(id)]
                return 1
            except couchdb.http.ResourceNotFound:
                return 0
        else:
            tablename = self.get_table(query)
            rows = self.select(query,[self.db[tablename]._id],{})
            ctable = self.connection[tablename]
            for row in rows:
                del ctable[str(row.id)]
            return len(rows)

    def update(self,tablename,query,fields):
        if not isinstance(query,Query):
            raise SyntaxError, "Not Supported"
        if query.first.type=='id' and query.op==self.EQ:
            id = query.second
            tablename = query.first.tablename
            ctable = self.connection[tablename]
            try:
                doc = ctable[str(id)]
                for key,value in fields:
                    doc[key.name] = self.represent(value,self.db[tablename][key.name].type)
                ctable.save(doc)
                return 1
            except couchdb.http.ResourceNotFound:
                return 0
        else:
            tablename = self.get_table(query)
            rows = self.select(query,[self.db[tablename]._id],{})
            ctable = self.connection[tablename]
            table = self.db[tablename]
            for row in rows:
                doc = ctable[str(row.id)]
                for key,value in fields:
                    doc[key.name] = self.represent(value,table[key.name].type)
                ctable.save(doc)
            return len(rows)

    def count(self,query,distinct=None):
        if distinct:
            raise RuntimeError, "COUNT DISTINCT not supported"
        if not isinstance(query,Query):
            raise SyntaxError, "Not Supported"
        tablename = self.get_table(query)
        rows = self.select(query,[self.db[tablename]._id],{})
        return len(rows)

def cleanup(text):
    """
    validates that the given text is clean: only contains [0-9a-zA-Z_]
    """

    if re.compile('[^0-9a-zA-Z_]').findall(text):
        raise SyntaxError, \
            'only [0-9a-zA-Z_] allowed in table and field names, received %s' \
            % text
    return text

class MongoDBAdapter(NoSQLAdapter):
    uploads_in_blob = True

    types = {
                'boolean': bool,
                'string': str,
                'text': str,
                'password': str,
                'blob': str,
                'upload': str,
                'integer': long,
                'bigint': long,
                'float': float,
                'double': float,
                'date': datetime.date,
                'time': datetime.time,
                'datetime': datetime.datetime,
                'id': long,
                'reference': long,
                'list:string': list,
                'list:integer': list,
                'list:reference': list,
        }

    def __init__(self,db,uri='mongodb://127.0.0.1:5984/db',
                 pool_size=0,folder=None,db_codec ='UTF-8',
                 credential_decoder=IDENTITY, driver_args={},
                 adapter_args={}):
        m=None
        try:
            #Since version 2
            import pymongo.uri_parser
            m = pymongo.uri_parser.parse_uri(uri)
        except ImportError:
            try:
                #before version 2 of pymongo
                import pymongo.connection
                m = pymongo.connection._parse_uri(uri)
            except ImportError:
                raise ImportError("Uriparser for mongodb is not available")
        except:
            raise SyntaxError("This type of uri is not supported by the mongodb uri parser")
        self.db = db
        self.uri = uri
        self.dbengine = 'mongodb'
        self.folder = folder
        db['_lastsql'] = ''
        self.db_codec = 'UTF-8'
        self.pool_size = pool_size
        #this is the minimum amount of replicates that it should wait for on insert/update
        self.minimumreplication = adapter_args.get('minimumreplication',0)
        #by default alle insert and selects are performand asynchronous, but now the default is
        #synchronous, except when overruled by either this default or function parameter
        self.safe = adapter_args.get('safe',True)


        if isinstance(m,tuple):
            m = {"database" : m[1]}
        if m.get('database')==None:
            raise SyntaxError("Database is required!")
        def connect(uri=self.uri,m=m):
            try:
                return pymongo.Connection(uri)[m.get('database')]
            except pymongo.errors.ConnectionFailure, inst:
                raise SyntaxError, "The connection to " + uri + " could not be made"
            except Exception, inst:
                if inst == "cannot specify database without a username and password":
                    raise SyntaxError("You are probebly running version 1.1 of pymongo which contains a bug which requires authentication. Update your pymongo.")
                else:
                    raise SyntaxError("This is not an official Mongodb uri (http://www.mongodb.org/display/DOCS/Connections) Error : %s" % inst)
        self.pool_connection(connect,cursor=False)
        self.after_connection()



    def represent(self, obj, fieldtype):
        value = NoSQLAdapter.represent(self, obj, fieldtype)
        if fieldtype  =='date':
            if value == None:
                return value
            t = datetime.time(0, 0, 0)#this piece of data can be stripped of based on the fieldtype
            return datetime.datetime.combine(value, t) #mongodb doesn't has a date object and so it must datetime, string or integer
        elif fieldtype == 'time':
            if value == None:
                return value
            d = datetime.date(2000, 1, 1) #this piece of data can be stripped of based on the fieldtype
            return datetime.datetime.combine(d, value) #mongodb doesn't has a  time object and so it must datetime, string or integer
        elif fieldtype == 'list:string' or fieldtype == 'list:integer' or fieldtype == 'list:reference':
            return value #raise SyntaxError, "Not Supported"
        return value

    #Safe determines whether a asynchronious request is done or a synchronious action is done
    #For safety, we use by default synchronious requests
    def insert(self,table,fields,safe=None):
        if safe==None:
            safe=self.safe
        ctable = self.connection[table._tablename]
        values = dict((k.name,self.represent(v,table[k.name].type)) for k,v in fields)
        ctable.insert(values,safe=safe)
        return int(str(values['_id']), 16)

    def create_table(self, table, migrate=True, fake_migrate=False, polymodel=None, isCapped=False):
        if isCapped:
            raise RuntimeError, "Not implemented"
        else:
            pass

    def count(self,query,distinct=None,snapshot=True):
        if distinct:
            raise RuntimeError, "COUNT DISTINCT not supported"
        if not isinstance(query,Query):
            raise SyntaxError, "Not Supported"
        tablename = self.get_table(query)
        return int(self.select(query,[self.db[tablename]._id],{},count=True,snapshot=snapshot)['count'])
        #Maybe it would be faster if we just implemented the pymongo .count() function which is probably quicker?
        # therefor call __select() connection[table].find(query).count() Since this will probably reduce the return set?

    def expand(self, expression, field_type=None):
        import pymongo.objectid
        #if isinstance(expression,Field):
        #    if expression.type=='id':
        #        return {_id}"
        if isinstance(expression, Query):
            print "in expand and this is a query"
            # any query using 'id':=
            #   set name as _id (as per pymongo/mongodb primary key)
            #   convert second arg to an objectid field (if its not already)
            #   if second arg is 0 convert to objectid
            if isinstance(expression.first,Field) and expression.first.type == 'id':
                expression.first.name = '_id'
                if expression.second != 0 and not isinstance(expression.second,pymongo.objectid.ObjectId):
                    if isinstance(expression.second,int):
                        try:
                            #Because the reference field is by default an integer and therefore this must be an integer to be able to work with other databases
                            expression.second = pymongo.objectid.ObjectId(("%X" % expression.second))
                        except:
                            raise SyntaxError, 'The second argument must by an integer that can represent an objectid.'
                    else:
                        try:
                            #But a direct id is also possible
                            expression.second = pymongo.objectid.ObjectId(expression.second)
                        except:
                            raise SyntaxError, 'second argument must be of type bson.objectid.ObjectId or an objectid representable integer'
                elif expression.second == 0:
                    expression.second = pymongo.objectid.ObjectId('000000000000000000000000')
                return expression.op(expression.first, expression.second)
        if isinstance(expression, Field):
            if expression.type=='id':
                return "_id"
            else:
                return expression.name
            #return expression
        elif isinstance(expression, (Expression, Query)):
            if not expression.second is None:
                return expression.op(expression.first, expression.second)
            elif not expression.first is None:
                return expression.op(expression.first)
            elif not isinstance(expression.op, str):
                return expression.op()
            else:
                return expression.op
        elif field_type:
            return str(self.represent(expression,field_type))
        elif isinstance(expression,(list,tuple)):
            return ','.join(self.represent(item,field_type) for item in expression)
        else:
            return expression

    def _select(self,query,fields,attributes):
        try:
            from bson.son import SON
        except ImportError:
            from pymongo.son import SON

        for key in set(attributes.keys())-set(('limitby','orderby')):
            raise SyntaxError, 'invalid select attribute: %s' % key

        new_fields=[]
        mongosort_list = []

        # try an orderby attribute
        orderby = attributes.get('orderby', False)
        limitby = attributes.get('limitby', False)
        #distinct = attributes.get('distinct', False)
        if orderby:
            #print "in if orderby %s" % orderby
            if isinstance(orderby, (list, tuple)):
                orderby = xorify(orderby)

            # !!!! need to add 'random'
            for f in self.expand(orderby).split(','):
                if f.startswith('-'):
                    mongosort_list.append((f[1:],-1))
                else:
                    mongosort_list.append((f,1))

        if limitby:
            limitby_skip, limitby_limit = limitby
        else:
            limitby_skip = limitby_limit = 0

        mongofields_dict = SON()
        mongoqry_dict = {}
        for item in fields:
            if isinstance(item,SQLALL):
                new_fields += item._table
            else:
                new_fields.append(item)
        fields = new_fields
        if isinstance(query,Query):
            tablename = self.get_table(query)
        elif len(fields) != 0:
            tablename = fields[0].tablename
        else:
            raise SyntaxError, "The table name could not be found in the query nor from the select statement."
        mongoqry_dict = self.expand(query)
        fields = fields or self.db[tablename]
        for field in fields:
            mongofields_dict[field.name] = 1
        return tablename, mongoqry_dict, mongofields_dict, \
            mongosort_list, limitby_limit, limitby_skip

    # need to define all the 'sql' methods gt,lt etc....

    def select(self,query,fields,attributes,count=False,snapshot=False):
        tablename, mongoqry_dict, mongofields_dict, \
        mongosort_list, limitby_limit, limitby_skip = \
            self._select(query,fields,attributes)
        ctable = self.connection[tablename]
        if count:
            return {'count' : ctable.find(
                    mongoqry_dict, mongofields_dict,
                    skip=limitby_skip, limit=limitby_limit,
                    sort=mongosort_list, snapshot=snapshot).count()}
        else:
            mongo_list_dicts = ctable.find(
                mongoqry_dict, mongofields_dict,
                skip=limitby_skip, limit=limitby_limit,
                sort=mongosort_list, snapshot=snapshot) # pymongo cursor object
        print "mongo_list_dicts=%s" % mongo_list_dicts
        rows = []
        ### populate row in proper order
        colnames = [field.name for field in fields]
        for k,record in enumerate(mongo_list_dicts):
            row=[]
            for colname in colnames:
                column = '_id' if colname=='id' else colname
                if column in record:
                    if column == '_id' and isinstance(
                        record[column],pymongo.objectid.ObjectId):
                        value = int(str(record[column]),16)
                    elif column != '_id':
                        value = record[column]
                    else:
                        value = None
                else:
                    value = None
                row.append(value)
            rows.append(row)
        processor = attributes.get('processor',self.parse)
        return processor(rows,fields,colnames,False)

    def INVERT(self,first):
        #print "in invert first=%s" % first
        return '-%s' % self.expand(first)

    def drop(self, table, mode=''):
        ctable = self.connection[table._tablename]
        ctable.drop()


    def truncate(self,table,mode,safe=None):
        if safe==None:
            safe=self.safe
        ctable = self.connection[table._tablename]
        ctable.remove(None, safe=True)

    #the update function should return a string
    def oupdate(self,tablename,query,fields):
        if not isinstance(query,Query):
            raise SyntaxError, "Not Supported"
        filter = None
        if query:
            filter = self.expand(query)
        f_v = []


        modify = { '$set' : dict(((k.name,self.represent(v,k.type)) for k,v in fields)) }
        return modify,filter

    #TODO implement update
    #TODO implement set operator
    #TODO implement find and modify
    #todo implement complex update
    def update(self,tablename,query,fields,safe=None):
        if safe==None:
            safe=self.safe
        #return amount of adjusted rows or zero, but no exceptions related not finding the result
        if not isinstance(query,Query):
            raise RuntimeError, "Not implemented"
        amount = self.count(query,False)
        modify,filter = self.oupdate(tablename,query,fields)
        try:
            if safe:
                return self.connection[tablename].update(filter,modify,multi=True,safe=safe).n
            else:
                amount =self.count(query)
                self.connection[tablename].update(filter,modify,multi=True,safe=safe)
                return amount
        except:
            #TODO Reverse update query to verifiy that the query succeded
            return 0
    """
    An special update operator that enables the update of specific field
    return a dict
    """



    #this function returns a dict with the where clause and update fields
    def _update(self,tablename,query,fields):
        return str(self.oupdate(tablename,query,fields))

    def bulk_insert(self, table, items):
        return [self.insert(table,item) for item in items]

    #TODO This will probably not work:(
    def NOT(self, first):
        result = {}
        result["$not"] = self.expand(first)
        return result

    def AND(self,first,second):
        f = self.expand(first)
        s = self.expand(second)
        f.update(s)
        return f

    def OR(self,first,second):
        # pymongo expects: .find( {'$or' : [{'name':'1'}, {'name':'2'}] } )
        result = {}
        f = self.expand(first)
        s = self.expand(second)
        result['$or'] = [f,s]
        return result

    def BELONGS(self, first, second):
        if isinstance(second, str):
            return {self.expand(first) : {"$in" : [ second[:-1]]} }
        elif second==[] or second==():
            return {1:0}
        items = [self.expand(item, first.type) for item in second]
        return {self.expand(first) : {"$in" : items} }

    def LIKE(self, first, second):
        #escaping regex operators?
        return {self.expand(first) : ('%s' % self.expand(second, 'string').replace('%','/'))}

    def STARTSWITH(self, first, second):
        #escaping regex operators?
        return {self.expand(first) : ('/^%s/' % self.expand(second, 'string'))}

    def ENDSWITH(self, first, second):
        #escaping regex operators?
        return {self.expand(first) : ('/%s^/' % self.expand(second, 'string'))}

    def CONTAINS(self, first, second):
        #There is a technical difference, but mongodb doesn't support that, but the result will be the same
        return {self.expand(first) : ('/%s/' % self.expand(second, 'string'))}

    def EQ(self,first,second):
        result = {}
        #if second is None:
            #return '(%s == null)' % self.expand(first)
        #return '(%s == %s)' % (self.expand(first),self.expand(second,first.type))
        result[self.expand(first)] = self.expand(second)
        return result

    def NE(self, first, second=None):
        print "in NE"
        result = {}
        result[self.expand(first)] = {'$ne': self.expand(second)}
        return result

    def LT(self,first,second=None):
        if second is None:
            raise RuntimeError, "Cannot compare %s < None" % first
        print "in LT"
        result = {}
        result[self.expand(first)] = {'$lt': self.expand(second)}
        return result

    def LE(self,first,second=None):
        if second is None:
            raise RuntimeError, "Cannot compare %s <= None" % first
        print "in LE"
        result = {}
        result[self.expand(first)] = {'$lte': self.expand(second)}
        return result

    def GT(self,first,second):
        print "in GT"
        #import pymongo.objectid
        result = {}
        #if expanded_first == '_id':
            #if expanded_second != 0 and not isinstance(second,pymongo.objectid.ObjectId):
                #raise SyntaxError, 'second argument must be of type bson.objectid.ObjectId'
            #elif expanded_second == 0:
                #expanded_second = pymongo.objectid.ObjectId('000000000000000000000000')
        result[self.expand(first)] = {'$gt': self.expand(second)}
        return result

    def GE(self,first,second=None):
        if second is None:
            raise RuntimeError, "Cannot compare %s >= None" % first
        print "in GE"
        result = {}
        result[self.expand(first)] = {'$gte': self.expand(second)}
        return result

    def ADD(self, first, second):
        raise NotImplementedError, "This must yet be replaced with javescript in order to accomplish this. Sorry"
        return '%s + %s' % (self.expand(first), self.expand(second, first.type))

    def SUB(self, first, second):
        raise NotImplementedError, "This must yet be replaced with javescript in order to accomplish this. Sorry"
        return '(%s - %s)' % (self.expand(first), self.expand(second, first.type))

    def MUL(self, first, second):
        raise NotImplementedError, "This must yet be replaced with javescript in order to accomplish this. Sorry"
        return '(%s * %s)' % (self.expand(first), self.expand(second, first.type))

    def DIV(self, first, second):
        raise NotImplementedError, "This must yet be replaced with javescript in order to accomplish this. Sorry"
        return '(%s / %s)' % (self.expand(first), self.expand(second, first.type))

    def MOD(self, first, second):
        raise NotImplementedError, "This must yet be replaced with javescript in order to accomplish this. Sorry"
        return '(%s %% %s)' % (self.expand(first), self.expand(second, first.type))

    def AS(self, first, second):
        raise NotImplementedError, "This must yet be replaced with javescript in order to accomplish this. Sorry"
        return '%s AS %s' % (self.expand(first), second)

    #We could implement an option that simulates a full featured SQL database. But I think the option should be set explicit or implemented as another library.
    def ON(self, first, second):
        raise NotImplementedError, "This is not possible in NoSQL, but can be simulated with a wrapper."
        return '%s ON %s' % (self.expand(first), self.expand(second))

    def COMMA(self, first, second):
        return '%s, %s' % (self.expand(first), self.expand(second))

    def bulk_insert(self, table, items):
        return [self.insert(table,item) for item in items]

    #TODO This will probably not work:(
    def NOT(self, first):
        result = {}
        result["$not"] = self.expand(first)
        return result

    def AND(self,first,second):
        f = self.expand(first)
        s = self.expand(second)
        f.update(s)
        return f

    def OR(self,first,second):
        # pymongo expects: .find( {'$or' : [{'name':'1'}, {'name':'2'}] } )
        result = {}
        f = self.expand(first)
        s = self.expand(second)
        result['$or'] = [f,s]
        return result

    def BELONGS(self, first, second):
        if isinstance(second, str):
            return {self.expand(first) : {"$in" : [ second[:-1]]} }
        elif second==[] or second==():
            return {1:0}
        items = [self.expand(item, first.type) for item in second]
        return {self.expand(first) : {"$in" : items} }

    #TODO verify full compatibilty with official SQL Like operator
    def LIKE(self, first, second):
        import re
        return {self.expand(first) : {'$regex' : re.escape(self.expand(second, 'string')).replace('%','.*')}}

    #TODO verify full compatibilty with official SQL Like operator
    def STARTSWITH(self, first, second):
        #TODO  Solve almost the same problem as with endswith
        import re
        return {self.expand(first) : {'$regex' : '^' + re.escape(self.expand(second, 'string'))}}

    #TODO verify full compatibilty with official SQL Like operator
    def ENDSWITH(self, first, second):
        #escaping regex operators?
        #TODO if searched for a name like zsa_corbitt and the function is endswith('a') then this is also returned. Aldo it end with a t
        import re
        return {self.expand(first) : {'$regex' : re.escape(self.expand(second, 'string')) + '$'}}

    #TODO verify full compatibilty with official oracle contains operator
    def CONTAINS(self, first, second):
        #There is a technical difference, but mongodb doesn't support that, but the result will be the same
        #TODO contains operators need to be transformed to Regex
        return {self.expand(first) : {' $regex' : ".*" + re.escape(self.expand(second, 'string')) + ".*"}}

    def EQ(self,first,second):
        result = {}
        #if second is None:
            #return '(%s == null)' % self.expand(first)
        #return '(%s == %s)' % (self.expand(first),self.expand(second,first.type))
        result[self.expand(first)] = self.expand(second)
        return result

    def NE(self, first, second=None):
        print "in NE"
        result = {}
        result[self.expand(first)] = {'$ne': self.expand(second)}
        return result

    def LT(self,first,second=None):
        if second is None:
            raise RuntimeError, "Cannot compare %s < None" % first
        print "in LT"
        result = {}
        result[self.expand(first)] = {'$lt': self.expand(second)}
        return result

    def LE(self,first,second=None):
        if second is None:
            raise RuntimeError, "Cannot compare %s <= None" % first
        print "in LE"
        result = {}
        result[self.expand(first)] = {'$lte': self.expand(second)}
        return result

    def GT(self,first,second):
        print "in GT"
        #import pymongo.objectid
        result = {}
        #if expanded_first == '_id':
            #if expanded_second != 0 and not isinstance(second,pymongo.objectid.ObjectId):
                #raise SyntaxError, 'second argument must be of type bson.objectid.ObjectId'
            #elif expanded_second == 0:
                #expanded_second = pymongo.objectid.ObjectId('000000000000000000000000')
        result[self.expand(first)] = {'$gt': self.expand(second)}
        return result

    def GE(self,first,second=None):
        if second is None:
            raise RuntimeError, "Cannot compare %s >= None" % first
        print "in GE"
        result = {}
        result[self.expand(first)] = {'$gte': self.expand(second)}
        return result

    #TODO javascript has math
    def ADD(self, first, second):
        raise NotImplementedError, "This must yet be replaced with javescript in order to accomplish this. Sorry"
        return '%s + %s' % (self.expand(first), self.expand(second, first.type))

    #TODO javascript has math
    def SUB(self, first, second):
        raise NotImplementedError, "This must yet be replaced with javescript in order to accomplish this. Sorry"
        return '(%s - %s)' % (self.expand(first), self.expand(second, first.type))

    #TODO javascript has math
    def MUL(self, first, second):
        raise NotImplementedError, "This must yet be replaced with javescript in order to accomplish this. Sorry"
        return '(%s * %s)' % (self.expand(first), self.expand(second, first.type))
        #TODO javascript has math

    def DIV(self, first, second):
        raise NotImplementedError, "This must yet be replaced with javescript in order to accomplish this. Sorry"
        return '(%s / %s)' % (self.expand(first), self.expand(second, first.type))
    #TODO javascript has math
    def MOD(self, first, second):
        raise NotImplementedError, "This must yet be replaced with javescript in order to accomplish this. Sorry"
        return '(%s %% %s)' % (self.expand(first), self.expand(second, first.type))

    #TODO javascript can do this
    def AS(self, first, second):
        raise NotImplementedError, "This must yet be replaced with javescript in order to accomplish this. Sorry"
        return '%s AS %s' % (self.expand(first), second)

    #We could implement an option that simulates a full featured SQL database. But I think the option should be set explicit or implemented as another library.
    def ON(self, first, second):
        raise NotImplementedError, "This is not possible in NoSQL, but can be simulated with a wrapper."
        return '%s ON %s' % (self.expand(first), self.expand(second))

    #TODO is this used in mongodb?
    def COMMA(self, first, second):
        return '%s, %s' % (self.expand(first), self.expand(second))



class IMAPAdapter(NoSQLAdapter):
    """ IMAP server adapter

      This class is intended as an interface with
    email IMAP servers to perform simple queries in the
    web2py DAL query syntax, so email read, search and
    other related IMAP mail services (as those implemented
    by brands like Google(r), and Yahoo!(r)
    can be managed from web2py applications.

    The code uses examples by Yuji Tomita on this post:
    http://yuji.wordpress.com/2011/06/22/python-imaplib-imap-example-with-gmail/#comment-1137
    and is based in docs for Python imaplib, python email
    and email IETF's (i.e. RFC2060 and RFC3501)

    This adapter was tested with a small set of operations with Gmail(r). Other
    services requests could raise command syntax and response data issues.

    It creates its table and field names "statically",
    meaning that the developer should leave the table and field
    definitions to the DAL instance by calling the adapter's
    .define_tables() method. The tables are defined with the
    IMAP server mailbox list information.

    .define_tables() returns a dictionary mapping dal tablenames
    to the server mailbox names with the following structure:
    
    {<tablename>: str <server mailbox name>}

    Here is a list of supported fields:

    Field       Type            Description
    ################################################################
    uid         string
    answered    boolean        Flag
    created     date
    content     list:string    A list of text or html parts
    to          string
    cc          string
    bcc         string
    size        integer        the amount of octets of the message*
    deleted     boolean        Flag
    draft       boolean        Flag
    flagged     boolean        Flag
    sender      string
    recent      boolean        Flag
    seen        boolean        Flag
    subject     string
    mime        string         The mime header declaration
    email       string         The complete RFC822 message**
    attachments list:string    Each non text decoded part as string

    *At the application side it is measured as the length of the RFC822
    message string

    WARNING: As row id's are mapped to email sequence numbers,
    make sure your imap client web2py app does not delete messages
    during select or update actions, to prevent
    updating or deleting different messages.
    Sequence numbers change whenever the mailbox is updated.
    To avoid this sequence numbers issues, it is recommended the use
    of uid fields in query references (although the update and delete
    in separate actions rule still applies).

    # This is the code recommended to start imap support
    # at the app's model:

    imapdb = DAL("imap://user:password@server:port", pool_size=1) # port 993 for ssl
    imapdb.define_tables()

    Here is an (incomplete) list of possible imap commands:

    # Count today's unseen messages
    # smaller than 6000 octets from the
    # inbox mailbox

    q = imapdb.INBOX.seen == False
    q &= imapdb.INBOX.created == datetime.date.today()
    q &= imapdb.INBOX.size < 6000
    unread = imapdb(q).count()

    # Fetch last query messages
    rows = imapdb(q).select()

    # it is also possible to filter query select results with limitby and
    # sequences of mailbox fields

    set.select(<fields sequence>, limitby=(<int>, <int>))

    # Mark last query messages as seen
    messages = [row.uid for row in rows]
    seen = imapdb(imapdb.INBOX.uid.belongs(messages)).update(seen=True)

    # Delete messages in the imap database that have mails from mr. Gumby

    deleted = 0
    for mailbox in imapdb.tables
        deleted += imapdb(imapdb[mailbox].sender.contains("gumby")).delete()

    # It is possible also to mark messages for deletion instead of ereasing them
    # directly with set.update(deleted=True)


    # This objects give access
    # to the adapter auto mailbox
    # mapped names (which native
    # mailbox has what table name)

    db.mailboxes <dict> # tablename, server native name
    db.mailbox_names <dict> # server native name, tablename

    """

    types = {
                'string': str,
                'text': str,
                'date': datetime.date,
                'datetime': datetime.datetime,
                'id': long,
                'boolean': bool,
                'integer': int,
                'bigint': long,
                'blob': str,
                'list:string': str,
        }

    dbengine = 'imap'
    driver = globals().get('imaplib',None)

    def __init__(self,
                 db,
                 uri,
                 pool_size=0,
                 folder=None,
                 db_codec ='UTF-8',
                 credential_decoder=IDENTITY,
                 driver_args={},
                 adapter_args={}):

        # db uri: user@example.com:password@imap.server.com:123
        # TODO: max size adapter argument for preventing large mail transfers

        uri = uri.split("://")[1]
        self.db = db
        self.uri = uri
        self.pool_size=pool_size
        self.folder = folder
        self.db_codec = db_codec
        self.credential_decoder = credential_decoder
        self.driver_args = driver_args
        self.adapter_args = adapter_args
        self.mailbox_size = None
        self.charset = sys.getfilesystemencoding()
        # imap class
        self.imap4 = None

        """ MESSAGE is an identifier for sequence number"""

        self.flags = ['\\Deleted', '\\Draft', '\\Flagged',
                      '\\Recent', '\\Seen', '\\Answered']
        self.search_fields = {
            'id': 'MESSAGE', 'created': 'DATE',
            'uid': 'UID', 'sender': 'FROM',
            'to': 'TO', 'cc': 'CC',
            'bcc': 'BCC', 'content': 'TEXT',
            'size': 'SIZE', 'deleted': '\\Deleted',
            'draft': '\\Draft', 'flagged': '\\Flagged',
            'recent': '\\Recent', 'seen': '\\Seen',
            'subject': 'SUBJECT', 'answered': '\\Answered',
            'mime': None, 'email': None,
            'attachments': None
            }

        db['_lastsql'] = ''

        m = re.compile('^(?P<user>[^:]+)(\:(?P<password>[^@]*))?@(?P<host>[^\:@]+)(\:(?P<port>[0-9]+))?$').match(uri)
        user = m.group('user')
        password = m.group('password')
        host = m.group('host')
        port = int(m.group('port'))
        over_ssl = False
        if port==993:
            over_ssl = True

        driver_args.update(dict(host=host,port=port, password=password, user=user))
        def connect(driver_args=driver_args):
            # it is assumed sucessful authentication alLways
            # TODO: support direct connection and login tests
            if over_ssl:
                self.imap4 = self.driver.IMAP4_SSL
            else:
                self.imap4 = self.driver.IMAP4
            connection = self.imap4(driver_args["host"], driver_args["port"])
            data = connection.login(driver_args["user"], driver_args["password"])
            
            # static mailbox list
            connection.mailbox_names = None

            # dummy cursor function
            connection.cursor = lambda : True

            return connection

        self.db.define_tables = self.define_tables
        self.pool_connection(connect)
        # self.after_connection()

    def pool_connection(self, f, cursor=True):
        """
        IMAP4 Pool connection method

        imap connection lacks of self cursor command.
        A custom command should be provided as a replacement
        for connection pooling to prevent uncaught remote session
        closing

        """
        if not self.pool_size:
            self.connection = f()
            self.cursor = cursor and self.connection.cursor()
        else:
            uri = self.uri
            while True:
                sql_locker.acquire()
                if not uri in ConnectionPool.pools:
                    ConnectionPool.pools[uri] = []
                if ConnectionPool.pools[uri]:
                    self.connection = ConnectionPool.pools[uri].pop()
                    sql_locker.release()
                    self.cursor = cursor and self.connection.cursor()
                    if self.cursor and self.check_active_connection:
                        try:
                            # check if connection is alive or close it
                            result, data = self.connection.list()
                        except:
                            # Possible connection reset error
                            # TODO: read exception class
                            self.connection = f()
                    break
                else:
                    sql_locker.release()
                    self.connection = f()
                    self.cursor = cursor and self.connection.cursor()
                    break

        if not hasattr(thread,'instances'):
            thread.instances = []
        thread.instances.append(self)

    def get_last_message(self, tablename):
        last_message = None
        # request mailbox list to the server
        # if needed
        if not isinstance(self.connection.mailbox_names, dict):
            self.get_mailboxes()
        try:
            result = self.connection.select(self.connection.mailbox_names[tablename])
            last_message = int(result[1][0])
        except (IndexError, ValueError, TypeError, KeyError), e:
            logger.debug("Error retrieving the last mailbox sequence number. %s" % str(e))
        return last_message

    def get_uid_bounds(self, tablename):
        if not isinstance(self.connection.mailbox_names, dict):
            self.get_mailboxes()
        # fetch first and last messages
        # return (first, last) messages uid's
        last_message = self.get_last_message(tablename)
        result, data = self.connection.uid("search", None, "(ALL)")
        uid_list = data[0].strip().split()
        if len(uid_list) <= 0:
            return None
        else:
            return (uid_list[0], uid_list[-1])

    def convert_date(self, date, add=None):
        if add is None:
            add = datetime.timedelta()
        """ Convert a date object to a string
        with d-Mon-Y style for IMAP or the inverse
        case

        add <timedelta> adds to the date object
        """
        months = [None, "Jan","Feb","Mar","Apr","May","Jun",
                  "Jul", "Aug","Sep","Oct","Nov","Dec"]
        if isinstance(date, basestring):
            # Prevent unexpected date response format
            try:
                dayname, datestring = date.split(",")
            except (ValueError):
                logger.debug("Could not parse date text: %s" % date)
                return None
            date_list = datestring.strip().split()
            year = int(date_list[2])
            month = months.index(date_list[1])
            day = int(date_list[0])
            hms = [int(value) for value in date_list[3].split(":")]
            return datetime.datetime(year, month, day,
                                     hms[0], hms[1], hms[2]) + add
        elif isinstance(date, (datetime.datetime, datetime.date)):
            return (date + add).strftime("%d-%b-%Y")

        else:
            return None

    def encode_text(self, text, charset, errors="replace"):
        """ convert text for mail to unicode"""
        if text is None:
            text = ""
        else:
            if isinstance(text, str):
                if charset is not None:
                    text = unicode(text, charset, errors)
                else:
                    text = unicode(text, "utf-8", errors)
            else:
                raise Exception("Unsupported mail text type %s" % type(text))
        return text.encode("utf-8")

    def get_charset(self, message):
        charset = message.get_content_charset()
        return charset

    def reset_mailboxes(self):
        self.connection.mailbox_names = None
        self.get_mailboxes()

    def get_mailboxes(self):
        """ Query the mail database for mailbox names """
        mailboxes_list = self.connection.list()
        self.connection.mailbox_names = dict()
        mailboxes = list()
        x = 0
        for item in mailboxes_list[1]:
            x = x + 1
            item = item.strip()
            if not "NOSELECT" in item.upper():
                sub_items = item.split("\"")
                sub_items = [sub_item for sub_item in sub_items \
                if len(sub_item.strip()) > 0]
                mailbox = sub_items[len(sub_items) - 1]
                # remove unwanted characters and store original names
                # Don't allow leading non alphabetic characters
                mailbox_name = re.sub('^[_0-9]*', '', re.sub('[^_\w]','',re.sub('[/ ]','_',mailbox)))
                mailboxes.append(mailbox_name)
                self.connection.mailbox_names[mailbox_name] = mailbox

        return mailboxes

    def get_query_mailbox(self, query):
        nofield = True
        tablename = None
        attr = query
        while nofield:
            if hasattr(attr, "first"):
                attr = attr.first
                if isinstance(attr, Field):
                    return attr.tablename
                elif isinstance(attr, Query):
                    pass
                else:
                    return None
            else:
                return None
        return tablename

    def is_flag(self, flag):
        if self.search_fields.get(flag, None) in self.flags:
            return True
        else:
            return False

    def define_tables(self):
        """
        Auto create common IMAP fileds

        This function creates fields definitions "statically"
        meaning that custom fields as in other adapters should
        not be supported and definitions handled on a service/mode
        basis (local syntax for Gmail(r), Ymail(r)

        Returns a dictionary with tablename, server native mailbox name
        pairs.
        """
        if not isinstance(self.connection.mailbox_names, dict):
            self.get_mailboxes()
        mailboxes = self.connection.mailbox_names.keys()
        for mailbox_name in mailboxes:
            self.db.define_table("%s" % mailbox_name,
                            Field("uid", "string", writable=False),
                            Field("answered", "boolean"),
                            Field("created", "datetime", writable=False),
                            Field("content", "list:string", writable=False),
                            Field("to", "string", writable=False),
                            Field("cc", "string", writable=False),
                            Field("bcc", "string", writable=False),
                            Field("size", "integer", writable=False),
                            Field("deleted", "boolean"),
                            Field("draft", "boolean"),
                            Field("flagged", "boolean"),
                            Field("sender", "string", writable=False),
                            Field("recent", "boolean", writable=False),
                            Field("seen", "boolean"),
                            Field("subject", "string", writable=False),
                            Field("mime", "string", writable=False),
                            Field("email", "string", writable=False, readable=False),
                            Field("attachments", "list:string", writable=False, readable=False),
                            )
                            
        return self.connection.mailbox_names

    def create_table(self, *args, **kwargs):
        # not implemented
        logger.debug("Create table feature is not implemented for %s" % type(self))

    def _select(self,query,fields,attributes):
        """  Search and Fetch records and return web2py
        rows
        """

        if use_common_filters(query):
            query = self.common_filter(query, [self.get_query_mailbox(query),])

        # move this statement elsewhere (upper-level)
        import email
        import email.header
        decode_header = email.header.decode_header
        # get records from imap server with search + fetch
        # convert results to a dictionary
        tablename = None
        fetch_results = list()
        if isinstance(query, (Expression, Query)):
            tablename = self.get_table(query)
            mailbox = self.connection.mailbox_names.get(tablename, None)
            if isinstance(query, Expression):
                pass
            elif isinstance(query, Query):
                if mailbox is not None:
                    # select with readonly
                    selected = self.connection.select(mailbox, True)
                    self.mailbox_size = int(selected[1][0])
                    search_query = "(%s)" % str(query).strip()
                    search_result = self.connection.uid("search", None, search_query)
                    # Normal IMAP response OK is assumed (change this)
                    if search_result[0] == "OK":
                        # For "light" remote server responses just get the first
                        # ten records (change for non-experimental implementation)
                        # However, light responses are not guaranteed with this
                        # approach, just fewer messages.
                        # TODO: change limitby single to 2-tuple argument
                        limitby = attributes.get('limitby', None)
                        messages_set = search_result[1][0].split()
                        # descending order
                        messages_set.reverse()
                        if limitby is not None:
                            # TODO: asc/desc attributes
                            messages_set = messages_set[int(limitby[0]):int(limitby[1])]
                        # Partial fetches are not used since the email
                        # library does not seem to support it (it converts
                        # partial messages to mangled message instances)
                        imap_fields = "(RFC822)"
                        if len(messages_set) > 0:
                            # create fetch results object list
                            # fetch each remote message and store it in memmory
                            # (change to multi-fetch command syntax for faster
                            # transactions)
                            for uid in messages_set:
                                # fetch the RFC822 message body
                                typ, data = self.connection.uid("fetch", uid, imap_fields)
                                if typ == "OK":
                                    fr = {"message": int(data[0][0].split()[0]),
                                        "uid": int(uid),
                                        "email": email.message_from_string(data[0][1]),
                                        "raw_message": data[0][1]
                                        }
                                    fr["multipart"] = fr["email"].is_multipart()
                                    # fetch flags for the message
                                    ftyp, fdata = self.connection.uid("fetch", uid, "(FLAGS)")
                                    if ftyp == "OK":
                                        fr["flags"] = self.driver.ParseFlags(fdata[0])
                                        fetch_results.append(fr)
                                    else:
                                        # error retrieving the flags for this message
                                        pass
                                else:
                                    # error retrieving the message body
                                    pass

        elif isinstance(query, basestring):
            # not implemented
            pass
        else:
            pass

        imapqry_dict = {}
        imapfields_dict = {}

        if len(fields) == 1 and isinstance(fields[0], SQLALL):
            allfields = True
        elif len(fields) == 0:
            allfields = True
        else:
            allfields = False
        if allfields:
            fieldnames = ["%s.%s" % (tablename, field) for field in self.search_fields.keys()]
        else:
            fieldnames = ["%s.%s" % (tablename, field.name) for field in fields]

        for k in fieldnames:
            imapfields_dict[k] = k

        imapqry_list = list()
        imapqry_array = list()
        for fr in fetch_results:
            attachments = []
            content = []
            size = 0
            n = int(fr["message"])
            item_dict = dict()
            message = fr["email"]
            uid = fr["uid"]
            charset = self.get_charset(message)
            flags = fr["flags"]
            raw_message = fr["raw_message"]
            # Return messages data mapping static fields
            # and fetched results. Mapping should be made
            # outside the select function (with auxiliary
            # instance methods)

            # pending: search flags states trough the email message
            # instances for correct output

            if "%s.id" % tablename in fieldnames:
                item_dict["%s.id" % tablename] = n
            if "%s.created" % tablename in fieldnames:
                item_dict["%s.created" % tablename] = self.convert_date(message["Date"])
            if "%s.uid" % tablename in fieldnames:
                item_dict["%s.uid" % tablename] = uid
            if "%s.sender" % tablename in fieldnames:
                # If there is no encoding found in the message header
                # force utf-8 replacing characters (change this to
                # module's defaults). Applies to .sender, .to, .cc and .bcc fields
                #############################################################################
                # TODO: External function to manage encoding and decoding of message strings
                #############################################################################
                item_dict["%s.sender" % tablename] = self.encode_text(message["From"], charset)
            if "%s.to" % tablename in fieldnames:
                item_dict["%s.to" % tablename] = self.encode_text(message["To"], charset)
            if "%s.cc" % tablename in fieldnames:
                if "Cc" in message.keys():
                    item_dict["%s.cc" % tablename] = self.encode_text(message["Cc"], charset)
                else:
                    item_dict["%s.cc" % tablename] = ""
            if "%s.bcc" % tablename in fieldnames:
                if "Bcc" in message.keys():
                    item_dict["%s.bcc" % tablename] = self.encode_text(message["Bcc"], charset)
                else:
                    item_dict["%s.bcc" % tablename] = ""
            if "%s.deleted" % tablename in fieldnames:
                item_dict["%s.deleted" % tablename] = "\\Deleted" in flags
            if "%s.draft" % tablename in fieldnames:
                item_dict["%s.draft" % tablename] = "\\Draft" in flags
            if "%s.flagged" % tablename in fieldnames:
                item_dict["%s.flagged" % tablename] = "\\Flagged" in flags
            if "%s.recent" % tablename in fieldnames:
                item_dict["%s.recent" % tablename] = "\\Recent" in flags
            if "%s.seen" % tablename in fieldnames:
                item_dict["%s.seen" % tablename] = "\\Seen" in flags
            if "%s.subject" % tablename in fieldnames:
                subject = message["Subject"]
                decoded_subject = decode_header(subject)
                text = decoded_subject[0][0]
                encoding = decoded_subject[0][1]
                if encoding in (None, ""):
                    encoding = charset
                item_dict["%s.subject" % tablename] = self.encode_text(text, encoding)
            if "%s.answered" % tablename in fieldnames:
                item_dict["%s.answered" % tablename] = "\\Answered" in flags
            if "%s.mime" % tablename in fieldnames:
                item_dict["%s.mime" % tablename] = message.get_content_type()
            # Here goes the whole RFC822 body as an email instance
            # for controller side custom processing
            # The message is stored as a raw string
            # >> email.message_from_string(raw string)
            # returns a Message object for enhanced object processing
            if "%s.email" % tablename in fieldnames:
                item_dict["%s.email" % tablename] = self.encode_text(raw_message, charset)
            # Size measure as suggested in a Velocity Reviews post
            # by Tim Williams: "how to get size of email attachment"
            # Note: len() and server RFC822.SIZE reports doesn't match
            # To retrieve the server size for representation would add a new
            # fetch transaction to the process
            for part in message.walk():
                if "%s.attachments" % tablename in fieldnames:
                    if not "text" in part.get_content_maintype():
                        attachments.append(part.get_payload(decode=True))
                if "%s.content" % tablename in fieldnames:
                    if "text" in part.get_content_maintype():
                        payload = self.encode_text(part.get_payload(decode=True), charset)
                        content.append(payload)
                if "%s.size" % tablename in fieldnames:
                    if part is not None:
                        size += len(str(part))

            item_dict["%s.content" % tablename] = bar_encode(content)
            item_dict["%s.attachments" % tablename] = bar_encode(attachments)
            item_dict["%s.size" % tablename] = size

            imapqry_list.append(item_dict)

        # extra object mapping for the sake of rows object
        # creation (sends an array or lists)
        for item_dict in imapqry_list:
            imapqry_array_item = list()
            for fieldname in fieldnames:
                imapqry_array_item.append(item_dict[fieldname])
            imapqry_array.append(imapqry_array_item)

        return tablename, imapqry_array, fieldnames

    def select(self,query,fields,attributes):
        tablename, imapqry_array , fieldnames = self._select(query,fields,attributes)
        # parse result and return a rows object
        colnames = fieldnames
        processor = attributes.get('processor',self.parse)
        return processor(imapqry_array, fields, colnames)

    def update(self, tablename, query, fields):
        if use_common_filters(query):
            query = self.common_filter(query, [tablename,])

        mark = []
        unmark = []
        rowcount = 0
        query = str(query)
        if query:
            for item in fields:
                field = item[0]
                name = field.name
                value = item[1]
                if self.is_flag(name):
                    flag = self.search_fields[name]
                    if (value is not None) and (flag != "\\Recent"):
                        if value:
                            mark.append(flag)
                        else:
                            unmark.append(flag)

            result, data = self.connection.select(self.connection.mailbox_names[tablename])
            string_query = "(%s)" % query
            result, data = self.connection.search(None, string_query)
            store_list = [item.strip() for item in data[0].split() if item.strip().isdigit()]
            # change marked flags
            for number in store_list:
                result = None
                if len(mark) > 0:
                    result, data = self.connection.store(number, "+FLAGS", "(%s)" % " ".join(mark))
                if len(unmark) > 0:
                    result, data = self.connection.store(number, "-FLAGS", "(%s)" % " ".join(unmark))
                if result == "OK":
                    rowcount += 1
        return rowcount

    def count(self,query,distinct=None):
        counter = 0
        tablename = self.get_query_mailbox(query)
        if query and tablename is not None:
            if use_common_filters(query):
                query = self.common_filter(query, [tablename,])
            result, data = self.connection.select(self.connection.mailbox_names[tablename])
            string_query = "(%s)" % query
            result, data = self.connection.search(None, string_query)
            store_list = [item.strip() for item in data[0].split() if item.strip().isdigit()]
            counter = len(store_list)
        return counter

    def delete(self, tablename, query):
        counter = 0
        if query:
            if use_common_filters(query):
                query = self.common_filter(query, [tablename,])
            result, data = self.connection.select(self.connection.mailbox_names[tablename])
            string_query = "(%s)" % query
            result, data = self.connection.search(None, string_query)
            store_list = [item.strip() for item in data[0].split() if item.strip().isdigit()]
            for number in store_list:
                result, data = self.connection.store(number, "+FLAGS", "(\\Deleted)")
                if result == "OK":
                    counter += 1
            if counter > 0:
                result, data = self.connection.expunge()
        return counter

    def BELONGS(self, first, second):
        result = None
        name = self.search_fields[first.name]
        if name == "MESSAGE":
            values = [str(val) for val in second if str(val).isdigit()]
            result = "%s" % ",".join(values).strip()

        elif name == "UID":
            values = [str(val) for val in second if str(val).isdigit()]
            result = "UID %s" % ",".join(values).strip()

        else:
            raise Exception("Operation not supported")
        # result = "(%s %s)" % (self.expand(first), self.expand(second))
        return result

    def CONTAINS(self, first, second):
        result = None
        name = self.search_fields[first.name]

        if name in ("FROM", "TO", "SUBJECT", "TEXT"):
            result = "%s \"%s\"" % (name, self.expand(second))
        else:
            if first.name in ("cc", "bcc"):
                result = "%s \"%s\"" % (first.name.upper(), self.expand(second))
            elif first.name == "mime":
                result = "HEADER Content-Type \"%s\"" % self.expand(second)
            else:
                raise Exception("Operation not supported")
        return result

    def GT(self, first, second):
        result = None
        name = self.search_fields[first.name]
        if name == "MESSAGE":
            last_message = self.get_last_message(first.tablename)
            result = "%d:%d" % (int(self.expand(second)) + 1, last_message)
        elif name == "UID":
            # GT and LT may not return
            # expected sets depending on
            # the uid format implemented
            try:
                pedestal, threshold = self.get_uid_bounds(first.tablename)
            except TypeError, e:
                logger.debug("Error requesting uid bounds: %s", str(e))
                return ""
            try:
                lower_limit = int(self.expand(second)) + 1
            except (ValueError, TypeError), e:
                raise Exception("Operation not supported (non integer UID)")
            result = "UID %s:%s" % (lower_limit, threshold)
        elif name == "DATE":
            result = "SINCE %s" % self.convert_date(second, add=datetime.timedelta(1))
        elif name == "SIZE":
            result = "LARGER %s" % self.expand(second)
        else:
            raise Exception("Operation not supported")
        return result

    def GE(self, first, second):
        result = None
        name = self.search_fields[first.name]
        if name == "MESSAGE":
            last_message = self.get_last_message(first.tablename)
            result = "%s:%s" % (self.expand(second), last_message)
        elif name == "UID":
            # GT and LT may not return
            # expected sets depending on
            # the uid format implemented
            try:
                pedestal, threshold = self.get_uid_bounds(first.tablename)
            except TypeError, e:
                logger.debug("Error requesting uid bounds: %s", str(e))
                return ""
            lower_limit = self.expand(second)
            result = "UID %s:%s" % (lower_limit, threshold)
        elif name == "DATE":
            result = "SINCE %s" % self.convert_date(second)
        else:
            raise Exception("Operation not supported")
        return result

    def LT(self, first, second):
        result = None
        name = self.search_fields[first.name]
        if name == "MESSAGE":
            result = "%s:%s" % (1, int(self.expand(second)) - 1)
        elif name == "UID":
            try:
                pedestal, threshold = self.get_uid_bounds(first.tablename)
            except TypeError, e:
                logger.debug("Error requesting uid bounds: %s", str(e))
                return ""
            try:
                upper_limit = int(self.expand(second)) - 1
            except (ValueError, TypeError), e:
                raise Exception("Operation not supported (non integer UID)")
            result = "UID %s:%s" % (pedestal, upper_limit)
        elif name == "DATE":
            result = "BEFORE %s" % self.convert_date(second)
        elif name == "SIZE":
            result = "SMALLER %s" % self.expand(second)
        else:
            raise Exception("Operation not supported")
        return result

    def LE(self, first, second):
        result = None
        name = self.search_fields[first.name]
        if name == "MESSAGE":
            result = "%s:%s" % (1, self.expand(second))
        elif name == "UID":
            try:
                pedestal, threshold = self.get_uid_bounds(first.tablename)
            except TypeError, e:
                logger.debug("Error requesting uid bounds: %s", str(e))
                return ""
            upper_limit = int(self.expand(second))
            result = "UID %s:%s" % (pedestal, upper_limit)
        elif name == "DATE":
            result = "BEFORE %s" % self.convert_date(second, add=datetime.timedelta(1))
        else:
            raise Exception("Operation not supported")
        return result

    def NE(self, first, second):
        result = self.NOT(self.EQ(first, second))
        result =  result.replace("NOT NOT", "").strip()
        return result

    def EQ(self,first,second):
        name = self.search_fields[first.name]
        result = None
        if name is not None:
            if name == "MESSAGE":
                # query by message sequence number
                result = "%s" % self.expand(second)
            elif name == "UID":
                result = "UID %s" % self.expand(second)
            elif name == "DATE":
                result = "ON %s" % self.convert_date(second)

            elif name in self.flags:
                if second:
                    result = "%s" % (name.upper()[1:])
                else:
                    result = "NOT %s" % (name.upper()[1:])
            else:
                raise Exception("Operation not supported")
        else:
            raise Exception("Operation not supported")
        return result

    def AND(self, first, second):
        result = "%s %s" % (self.expand(first), self.expand(second))
        return result

    def OR(self, first, second):
        result = "OR %s %s" % (self.expand(first), self.expand(second))
        return "%s" % result.replace("OR OR", "OR")

    def NOT(self, first):
        result = "NOT %s" % self.expand(first)
        return result

########################################################################
# end of adapters
########################################################################

ADAPTERS = {
    'sqlite': SQLiteAdapter,
    'spatialite': SpatiaLiteAdapter,
    'sqlite:memory': SQLiteAdapter,
    'spatialite:memory': SpatiaLiteAdapter,
    'mysql': MySQLAdapter,
    'postgres': PostgreSQLAdapter,
    'postgres:psycopg2': PostgreSQLAdapter,
    'postgres:pg8000': PostgreSQLAdapter,
    'postgres2:psycopg2': NewPostgreSQLAdapter,
    'postgres2:pg8000': NewPostgreSQLAdapter,
    'oracle': OracleAdapter,
    'mssql': MSSQLAdapter,
    'mssql2': MSSQL2Adapter,
    'sybase': SybaseAdapter,
    'db2': DB2Adapter,
    'teradata': TeradataAdapter,
    'informix': InformixAdapter,
    'firebird': FireBirdAdapter,
    'firebird_embedded': FireBirdAdapter,
    'ingres': IngresAdapter,
    'ingresu': IngresUnicodeAdapter,
    'sapdb': SAPDBAdapter,
    'cubrid': CubridAdapter,
    'jdbc:sqlite': JDBCSQLiteAdapter,
    'jdbc:sqlite:memory': JDBCSQLiteAdapter,
    'jdbc:postgres': JDBCPostgreSQLAdapter,
    'gae': GoogleDatastoreAdapter, # discouraged, for backward compatibility
    'google:datastore': GoogleDatastoreAdapter,
    'google:sql': GoogleSQLAdapter,
    'couchdb': CouchDBAdapter,
    'mongodb': MongoDBAdapter,
    'imap': IMAPAdapter
}


def sqlhtml_validators(field):
    """
    Field type validation, using web2py's validators mechanism.

    makes sure the content of a field is in line with the declared
    fieldtype
    """
    if not have_validators:
        return []
    field_type, field_length = field.type, field.length
    if isinstance(field_type, SQLCustomType):
        if hasattr(field_type, 'validator'):
            return field_type.validator
        else:
            field_type = field_type.type
    elif not isinstance(field_type,str):
        return []
    requires=[]
    def ff(r,id):
        row=r(id)
        if not row:
            return id
        elif hasattr(r, '_format') and isinstance(r._format,str):
            return r._format % row
        elif hasattr(r, '_format') and callable(r._format):
            return r._format(row)
        else:
            return id
    if field_type == 'string':
        requires.append(validators.IS_LENGTH(field_length))
    elif field_type == 'text':
        requires.append(validators.IS_LENGTH(field_length))
    elif field_type == 'password':
        requires.append(validators.IS_LENGTH(field_length))
    elif field_type == 'double' or field_type == 'float':
        requires.append(validators.IS_FLOAT_IN_RANGE(-1e100, 1e100))
    elif field_type in ('integer','bigint'):
        requires.append(validators.IS_INT_IN_RANGE(-1e100, 1e100))
    elif field_type.startswith('decimal'):
        requires.append(validators.IS_DECIMAL_IN_RANGE(-10**10, 10**10))
    elif field_type == 'date':
        requires.append(validators.IS_DATE())
    elif field_type == 'time':
        requires.append(validators.IS_TIME())
    elif field_type == 'datetime':
        requires.append(validators.IS_DATETIME())
    elif field.db and field_type.startswith('reference') and \
            field_type.find('.') < 0 and \
            field_type[10:] in field.db.tables:
        referenced = field.db[field_type[10:]]
        def repr_ref(id, row=None, r=referenced, f=ff): return f(r, id)
        field.represent = field.represent or repr_ref
        if hasattr(referenced, '_format') and referenced._format:
            requires = validators.IS_IN_DB(field.db,referenced._id,
                                           referenced._format)
            if field.unique:
                requires._and = validators.IS_NOT_IN_DB(field.db,field)
            if field.tablename == field_type[10:]:
                return validators.IS_EMPTY_OR(requires)
            return requires
    elif field.db and field_type.startswith('list:reference') and \
            field_type.find('.') < 0 and \
            field_type[15:] in field.db.tables:
        referenced = field.db[field_type[15:]]
        def list_ref_repr(ids, row=None, r=referenced, f=ff):
            if not ids:
                return None
            refs = r._db(r._id.belongs(ids)).select(r._id)
            return (refs and ', '.join(str(f(r,ref.id)) for ref in refs) or '')
        field.represent = field.represent or list_ref_repr
        if hasattr(referenced, '_format') and referenced._format:
            requires = validators.IS_IN_DB(field.db,referenced._id,
                                           referenced._format,multiple=True)
        else:
            requires = validators.IS_IN_DB(field.db,referenced._id,
                                           multiple=True)
        if field.unique:
            requires._and = validators.IS_NOT_IN_DB(field.db,field)
        return requires
    elif field_type.startswith('list:'):
        def repr_list(values,row=None): return', '.join(str(v) for v in (values or []))
        field.represent = field.represent or repr_list
    if field.unique:
        requires.insert(0,validators.IS_NOT_IN_DB(field.db,field))
    sff = ['in', 'do', 'da', 'ti', 'de', 'bo']
    if field.notnull and not field_type[:2] in sff:
        requires.insert(0, validators.IS_NOT_EMPTY())
    elif not field.notnull and field_type[:2] in sff and requires:
        requires[-1] = validators.IS_EMPTY_OR(requires[-1])
    return requires


def bar_escape(item):
    return str(item).replace('|', '||')

def bar_encode(items):
    return '|%s|' % '|'.join(bar_escape(item) for item in items if str(item).strip())

def bar_decode_integer(value):
    if not hasattr(value,'split') and hasattr(value,'read'):
        value = value.read()
    return [int(x) for x in value.split('|') if x.strip()]

def bar_decode_string(value):
    return [x.replace('||', '|') for x in string_unpack.split(value[1:-1]) if x.strip()]


class Row(dict):

    """
    a dictionary that lets you do d['a'] as well as d.a
    this is only used to store a Row
    """

    def __getitem__(self, key):
        key=str(key)
        m = regex_table_field.match(key)
        if key in self.get('_extra',{}):
            return self._extra[key]
        elif m:
            try:
                return dict.__getitem__(self, m.group(1))[m.group(2)]
            except (KeyError,TypeError):
                key = m.group(2)
        return dict.__getitem__(self, key)

    def __call__(self,key):
        return self.__getitem__(key)

    def __setitem__(self, key, value):
        dict.__setitem__(self, str(key), value)

    def __getattr__(self, key):
        return self[key]

    def __setattr__(self, key, value):
        self[key] = value

    def __str__(self):
        ### this could be made smarter
        return '<Row ' + dict.__repr__(self) + '>'

    def __repr__(self):
        return '<Row ' + dict.__repr__(self) + '>'

    def __int__(self):
        return dict.__getitem__(self,'id')

    def __eq__(self,other):
        try:
            return self.as_dict() == other.as_dict()
        except AttributeError:
            return False

    def __ne__(self,other):
        return not (self == other)

    def __copy__(self):
        return Row(dict(self))

    def as_dict(self,datetime_to_str=False):
        SERIALIZABLE_TYPES = (str,unicode,int,long,float,bool,list)
        d = dict(self)
        for k in copy.copy(d.keys()):
            v=d[k]
            if d[k] is None:
                continue
            elif isinstance(v,Row):
                d[k]=v.as_dict()
            elif isinstance(v,Reference):
                d[k]=int(v)
            elif isinstance(v,decimal.Decimal):
                d[k]=float(v)
            elif isinstance(v, (datetime.date, datetime.datetime, datetime.time)):
                if datetime_to_str:
                    d[k] = v.isoformat().replace('T',' ')[:19]
            elif not isinstance(v,SERIALIZABLE_TYPES):
                del d[k]
        return d


def Row_unpickler(data):
    return Row(cPickle.loads(data))

def Row_pickler(data):
    return Row_unpickler, (cPickle.dumps(data.as_dict(datetime_to_str=False)),)

copy_reg.pickle(Row, Row_pickler, Row_unpickler)


################################################################################
# Everything below should be independent of the specifics of the database 
# and should work for RDBMs and some NoSQL databases
################################################################################

class SQLCallableList(list):
    def __call__(self):
        return copy.copy(self)

def smart_query(fields,text):
    if not isinstance(fields,(list,tuple)):
        fields = [fields]
    new_fields = []
    for field in fields:
        if isinstance(field,Field):
            new_fields.append(field)
        elif isinstance(field,Table):
            for ofield in field:
                new_fields.append(ofield)
        else:
            raise RuntimeError, "fields must be a list of fields"
    fields = new_fields
    field_map = {}
    for field in fields:
        n = field.name.lower()
        if not n in field_map:
            field_map[n] = field
        n = str(field).lower()
        if not n in field_map:
            field_map[n] = field
    re_constants = re.compile('(\"[^\"]*?\")|(\'[^\']*?\')')
    constants = {}
    i = 0
    while True:
        m = re_constants.search(text)
        if not m: break
        text = text[:m.start()]+('#%i' % i)+text[m.end():]
        constants[str(i)] = m.group()[1:-1]
        i+=1
    text = re.sub('\s+',' ',text).lower()
    for a,b in [('&','and'),
                ('|','or'),
                ('~','not'),
                ('==','='),
                ('<','<'),
                ('>','>'),
                ('<=','<='),
                ('>=','>='),
                ('<>','!='),
                ('=<','<='),
                ('=>','>='),
                ('=','='),
                (' less or equal than ','<='),
                (' greater or equal than ','>='),
                (' equal or less than ','<='),
                (' equal or greater than ','>='),
                (' less or equal ','<='),
                (' greater or equal ','>='),
                (' equal or less ','<='),
                (' equal or greater ','>='),
                (' not equal to ','!='),
                (' not equal ','!='),
                (' equal to ','='),
                (' equal ','='),
                (' equals ','!='),
                (' less than ','<'),
                (' greater than ','>'),
                (' starts with ','startswith'),
                (' ends with ','endswith'),
                (' is ','=')]:
        if a[0]==' ':
            text = text.replace(' is'+a,' %s ' % b)
        text = text.replace(a,' %s ' % b)
    text = re.sub('\s+',' ',text).lower()
    text = re.sub('(?P<a>[\<\>\!\=])\s+(?P<b>[\<\>\!\=])','\g<a>\g<b>',text)
    query = field = neg = op = logic = None
    for item in text.split():
        if field is None:
            if item == 'not':
                neg = True
            elif not neg and not logic and item in ('and','or'):
                logic = item
            elif item in field_map:
                field = field_map[item]
            else:
                raise RuntimeError, "Invalid syntax"
        elif not field is None and op is None:
            op = item
        elif not op is None:
            if item.startswith('#'):
                if not item[1:] in constants:
                    raise RuntimeError, "Invalid syntax"
                value = constants[item[1:]]
            else:
                value = item
                if field.type in ('text','string'): 
                    if op == '=': op = 'like'
            if op == '=': new_query = field==value
            elif op == '<': new_query = field<value
            elif op == '>': new_query = field>value
            elif op == '<=': new_query = field<=value
            elif op == '>=': new_query = field>=value
            elif op == '!=': new_query = field!=value
            elif field.type in ('text','string'):
                if op == 'contains': new_query = field.contains(value)
                elif op == 'like': new_query = field.like(value)
                elif op == 'startswith': new_query = field.startswith(value)
                elif op == 'endswith': new_query = field.endswith(value)
                else: raise RuntimeError, "Invalid operation"
            else: raise RuntimeError, "Invalid operation"
            if neg: new_query = ~new_query
            if query is None:
                query = new_query
            elif logic == 'and':
                query &= new_query
            elif logic == 'or':
                query |= new_query
            field = op = neg = logic = None
    return query


class DAL(dict):

    """
    an instance of this class represents a database connection

    Example::

       db = DAL('sqlite://test.db')
       db.define_table('tablename', Field('fieldname1'),
                                    Field('fieldname2'))
    """

    @staticmethod
    def set_folder(folder):
        """
        # ## this allows gluon to set a folder for this thread
        # ## <<<<<<<<< Should go away as new DAL replaces old sql.py
        """
        BaseAdapter.set_folder(folder)

    @staticmethod
    def distributed_transaction_begin(*instances):
        if not instances:
            return
        thread_key = '%s.%s' % (socket.gethostname(), threading.currentThread())
        keys = ['%s.%i' % (thread_key, i) for (i,db) in instances]
        instances = enumerate(instances)
        for (i, db) in instances:
            if not db._adapter.support_distributed_transaction():
                raise SyntaxError, \
                    'distributed transaction not suported by %s' % db._dbname
        for (i, db) in instances:
            db._adapter.distributed_transaction_begin(keys[i])

    @staticmethod
    def distributed_transaction_commit(*instances):
        if not instances:
            return
        instances = enumerate(instances)
        thread_key = '%s.%s' % (socket.gethostname(), threading.currentThread())
        keys = ['%s.%i' % (thread_key, i) for (i,db) in instances]
        for (i, db) in instances:
            if not db._adapter.support_distributed_transaction():
                raise SyntaxError, \
                    'distributed transaction not suported by %s' % db._dbanme
        try:
            for (i, db) in instances:
                db._adapter.prepare(keys[i])
        except:
            for (i, db) in instances:
                db._adapter.rollback_prepared(keys[i])
            raise RuntimeError, 'failure to commit distributed transaction'
        else:
            for (i, db) in instances:
                db._adapter.commit_prepared(keys[i])
        return


    def __init__(self, uri='sqlite://dummy.db',
                 pool_size=0, folder=None,
                 db_codec='UTF-8', check_reserved=None,
                 migrate=True, fake_migrate=False,
                 migrate_enabled=True, fake_migrate_all=False,
                 decode_credentials=False, driver_args=None,
                 adapter_args=None, attempts=5, auto_import=False,
                 bigint_id=False,debug=False):
        """
        Creates a new Database Abstraction Layer instance.

        Keyword arguments:

        :uri: string that contains information for connecting to a database.
               (default: 'sqlite://dummy.db')
        :pool_size: How many open connections to make to the database object.
        :folder: <please update me>
        :db_codec: string encoding of the database (default: 'UTF-8')
        :check_reserved: list of adapters to check tablenames and column names
                         against sql reserved keywords. (Default None)

        * 'common' List of sql keywords that are common to all database types
                such as "SELECT, INSERT". (recommended)
        * 'all' Checks against all known SQL keywords. (not recommended)
                <adaptername> Checks against the specific adapters list of keywords
                (recommended)
        * '<adaptername>_nonreserved' Checks against the specific adapters
                list of nonreserved keywords. (if available)
        :migrate (defaults to True) sets default migrate behavior for all tables
        :fake_migrate (defaults to False) sets default fake_migrate behavior for all tables
        :migrate_enabled (defaults to True). If set to False disables ALL migrations
        :fake_migrate_all (defaults to False). If sets to True fake migrates ALL tables
        :attempts (defaults to 5). Number of times to attempt connecting
        """
        if not decode_credentials:
            credential_decoder = lambda cred: cred
        else:
            credential_decoder = lambda cred: urllib.unquote(cred)
        if folder:
            self.set_folder(folder)
        self._uri = uri
        self._pool_size = pool_size
        self._db_codec = db_codec
        self._lastsql = ''
        self._timings = []
        self._pending_references = {}
        self._request_tenant = 'request_tenant'
        self._common_fields = []
        self._referee_name = '%(table)s'
        self._bigint_id = bigint_id
        self._debug = debug
        self._migrated = []
        if not str(attempts).isdigit() or attempts < 0:
            attempts = 5
        if uri:
            uris = isinstance(uri,(list,tuple)) and uri or [uri]
            error = ''
            connected = False
            for k in range(attempts):
                for uri in uris:
                    try:
                        if is_jdbc and not uri.startswith('jdbc:'):
                            uri = 'jdbc:'+uri
                        self._dbname = regex_dbname.match(uri).group()
                        if not self._dbname in ADAPTERS:
                            raise SyntaxError, "Error in URI '%s' or database not supported" % self._dbname
                        # notice that driver args or {} else driver_args
                        # defaults to {} global, not correct
                        args = (self,uri,pool_size,folder,
                                db_codec, credential_decoder,
                                driver_args or {}, adapter_args or {})
                        self._adapter = ADAPTERS[self._dbname](*args)
                        if bigint_id:
                            types = ADAPTERS[self._dbname].types
                            self._adapter.types = copy.copy(types) # copy so multiple DAL() possible
                            if 'big-id' in types and 'reference' in types:
                                self._adapter.types['id'] = types['big-id']
                                self._adapter.types['reference'] = types['big-reference']
                        connected = True
                        break
                    except SyntaxError:
                        raise
                    except Exception, error:
                        tb = traceback.format_exc()
                        sys.stderr.write('DEBUG: connect attempt %i, connection error:\n%s' % (k, tb))
                if connected:
                    break
                else:
                    time.sleep(1)
            if not connected:
                raise RuntimeError, "Failure to connect, tried %d times:\n%s" % (attempts, tb)
        else:
            args = (self,'None',0,folder,db_codec)
            self._adapter = BaseAdapter(*args)
            migrate = fake_migrate = False
        adapter = self._adapter
        self._uri_hash = hashlib.md5(adapter.uri).hexdigest()
        self._tables = SQLCallableList()
        self.check_reserved = check_reserved
        if self.check_reserved:
            from reserved_sql_keywords import ADAPTERS as RSK
            self.RSK = RSK
        self._migrate = migrate
        self._fake_migrate = fake_migrate
        self._migrate_enabled = migrate_enabled
        self._fake_migrate_all = fake_migrate_all
        if auto_import:
            self.import_table_definitions(adapter.folder)

    @property
    def tables(self):
        return self._tables

    def import_table_definitions(self,path,migrate=False,fake_migrate=False):
        pattern = os.path.join(path,self._uri_hash+'_*.table')
        for filename in glob.glob(pattern):
            tfile = self._adapter.file_open(filename, 'r')
            try:
                sql_fields = cPickle.load(tfile)
                name = filename[len(pattern)-7:-6]
                mf = [(value['sortable'],Field(key,type=value['type'])) \
                          for key, value in sql_fields.items()]
                mf.sort(lambda a,b: cmp(a[0],b[0]))
                self.define_table(name,*[item[1] for item in mf],
                                  **dict(migrate=migrate,fake_migrate=fake_migrate))
            finally:
                self._adapter.file_close(tfile)

    def check_reserved_keyword(self, name):
        """
        Validates ``name`` against SQL keywords
        Uses self.check_reserve which is a list of
        operators to use.
        self.check_reserved
        ['common', 'postgres', 'mysql']
        self.check_reserved
        ['all']
        """
        for backend in self.check_reserved:
            if name.upper() in self.RSK[backend]:
                raise SyntaxError, 'invalid table/column name "%s" is a "%s" reserved SQL keyword' % (name, backend.upper())

    def __contains__(self, tablename):
        if self.has_key(tablename):
            return True
        else:
            return False

    def parse_as_rest(self,patterns,args,vars,queries=None,nested_select=True):
        """
        EXAMPLE:

db.define_table('person',Field('name'),Field('info'))
db.define_table('pet',Field('owner',db.person),Field('name'),Field('info'))

@request.restful()
def index():
    def GET(*args,**vars):
        patterns = [
            "/friends[person]",
            "/{friend.name.startswith}",
            "/{friend.name}/:field",
            "/{friend.name}/pets[pet.owner]",
            "/{friend.name}/pet[pet.owner]/{pet.name}",
            "/{friend.name}/pet[pet.owner]/{pet.name}/:field"
            ]
        parser = db.parse_as_rest(patterns,args,vars)
        if parser.status == 200:
            return dict(content=parser.response)
        else:
            raise HTTP(parser.status,parser.error)
    def POST(table_name,**vars):
        if table_name == 'person':
            return db.person.validate_and_insert(**vars)
        elif table_name == 'pet':
            return db.pet.validate_and_insert(**vars)
        else:
            raise HTTP(400)
    return locals()
        """

        db = self
        re1 = re.compile('^{[^\.]+\.[^\.]+(\.(lt|gt|le|ge|eq|ne|contains|startswith|year|month|day|hour|minute|second))?(\.not)?}$')
        re2 = re.compile('^.+\[.+\]$')

        def auto_table(table,base='',depth=0):
            patterns = []
            for field in db[table].fields:
                if base:
                    tag = '%s/%s' % (base,field.replace('_','-'))
                else:
                    tag = '/%s/%s' % (table.replace('_','-'),field.replace('_','-'))
                f = db[table][field]
                if not f.readable: continue
                if f.type=='id' or 'slug' in field or f.type.startswith('reference'):
                    tag += '/{%s.%s}' % (table,field)
                    patterns.append(tag)
                    patterns.append(tag+'/:field')
                elif f.type.startswith('boolean'):
                    tag += '/{%s.%s}' % (table,field)
                    patterns.append(tag)
                    patterns.append(tag+'/:field')
                elif f.type in ('float','double','integer','bigint'):
                    tag += '/{%s.%s.ge}/{%s.%s.lt}' % (table,field,table,field)
                    patterns.append(tag)
                    patterns.append(tag+'/:field')
                elif f.type.startswith('list:'):
                    tag += '/{%s.%s.contains}' % (table,field)
                    patterns.append(tag)
                    patterns.append(tag+'/:field')
                elif f.type in ('date','datetime'):
                    tag+= '/{%s.%s.year}' % (table,field)
                    patterns.append(tag)
                    patterns.append(tag+'/:field')
                    tag+='/{%s.%s.month}' % (table,field)
                    patterns.append(tag)
                    patterns.append(tag+'/:field')
                    tag+='/{%s.%s.day}' % (table,field)
                    patterns.append(tag)
                    patterns.append(tag+'/:field')
                if f.type in ('datetime','time'):
                    tag+= '/{%s.%s.hour}' % (table,field)
                    patterns.append(tag)
                    patterns.append(tag+'/:field')
                    tag+='/{%s.%s.minute}' % (table,field)
                    patterns.append(tag)
                    patterns.append(tag+'/:field')
                    tag+='/{%s.%s.second}' % (table,field)
                    patterns.append(tag)
                    patterns.append(tag+'/:field')
                if depth>0:
                    for rtable,rfield in db[table]._referenced_by:
                        tag+='/%s[%s.%s]' % (rtable,rtable,rfield)
                        patterns.append(tag)
                        patterns += auto_table(rtable,base=tag,depth=depth-1)
            return patterns

        if patterns=='auto':
            patterns=[]
            for table in db.tables:
                if not table.startswith('auth_'):
                    patterns.append('/%s[%s]' % (table,table))
                    patterns += auto_table(table,base='',depth=1)
        else:
            i = 0
            while i<len(patterns):
                pattern = patterns[i]
                tokens = pattern.split('/')
                if tokens[-1].startswith(':auto') and re2.match(tokens[-1]):
                    new_patterns = auto_table(tokens[-1][tokens[-1].find('[')+1:-1],
                                              '/'.join(tokens[:-1]))
                    patterns = patterns[:i]+new_patterns+patterns[i+1:]
                    i += len(new_patterns)
                else:
                    i += 1
        if '/'.join(args) == 'patterns':
            return Row({'status':200,'pattern':'list',
                        'error':None,'response':patterns})
        for pattern in patterns:
            otable=table=None
            if not isinstance(queries,dict):
                dbset=db(queries)
            i=0
            tags = pattern[1:].split('/')
            if len(tags)!=len(args):
                continue
            for tag in tags:
                if re1.match(tag):
                    # print 're1:'+tag
                    tokens = tag[1:-1].split('.')
                    table, field = tokens[0], tokens[1]
                    if not otable or table == otable:
                        if len(tokens)==2 or tokens[2]=='eq':
                            query = db[table][field]==args[i]
                        elif tokens[2]=='ne':
                            query = db[table][field]!=args[i]
                        elif tokens[2]=='lt':
                            query = db[table][field]<args[i]
                        elif tokens[2]=='gt':
                            query = db[table][field]>args[i]
                        elif tokens[2]=='ge':
                            query = db[table][field]>=args[i]
                        elif tokens[2]=='le':
                            query = db[table][field]<=args[i]
                        elif tokens[2]=='year':
                            query = db[table][field].year()==args[i]
                        elif tokens[2]=='month':
                            query = db[table][field].month()==args[i]
                        elif tokens[2]=='day':
                            query = db[table][field].day()==args[i]
                        elif tokens[2]=='hour':
                            query = db[table][field].hour()==args[i]
                        elif tokens[2]=='minute':
                            query = db[table][field].minutes()==args[i]
                        elif tokens[2]=='second':
                            query = db[table][field].seconds()==args[i]
                        elif tokens[2]=='startswith':
                            query = db[table][field].startswith(args[i])
                        elif tokens[2]=='contains':
                            query = db[table][field].contains(args[i])
                        else:
                            raise RuntimeError, "invalid pattern: %s" % pattern
                        if len(tokens)==4 and tokens[3]=='not':
                            query = ~query
                        elif len(tokens)>=4:
                            raise RuntimeError, "invalid pattern: %s" % pattern
                        if not otable and isinstance(queries,dict):
                            dbset = db(queries[table])
                        dbset=dbset(query)
                    else:
                        raise RuntimeError, "missing relation in pattern: %s" % pattern
                elif re2.match(tag) and args[i]==tag[:tag.find('[')]:
                    ref = tag[tag.find('[')+1:-1]
                    if '.' in ref and otable:
                        table,field = ref.split('.')
                        # print table,field
                        if nested_select:
                            try:
                                dbset=db(db[table][field].belongs(dbset._select(db[otable]._id)))
                            except ValueError:
                                return Row({'status':400,'pattern':pattern,
                                            'error':'invalid path','response':None})
                        else:
                            items = [item.id for item in dbset.select(db[otable]._id)]
                            dbset=db(db[table][field].belongs(items))
                    else:
                        table = ref
                        if not otable and isinstance(queries,dict):
                            dbset = db(queries[table])
                        dbset=dbset(db[table])
                elif tag==':field' and table:
                    # # print 're3:'+tag
                    field = args[i]
                    if not field in db[table]: break
                    # hand-built patterns should respect .readable=False as well
                    if not db[table][field].readable:
                        return Row({'status':418,'pattern':pattern,
                                    'error':'I\'m a teapot','response':None})
                    try:
                        item =  dbset.select(db[table][field],limitby=(0,1)).first()
                    except ValueError:
                        return Row({'status':400,'pattern':pattern,
                                    'error':'invalid path','response':None})
                    if not item:
                        return Row({'status':404,'pattern':pattern,
                                    'error':'record not found','response':None})
                    else:
                        return Row({'status':200,'response':item[field],
                                    'pattern':pattern})
                elif tag != args[i]:
                    break
                otable = table
                i += 1
                if i==len(tags) and table:
                    ofields = vars.get('order',db[table]._id.name).split('|')
                    try:
                        orderby = [db[table][f] if not f.startswith('~') else ~db[table][f[1:]] for f in ofields]
                    except KeyError:
                        return Row({'status':400,'error':'invalid orderby','response':None})
                    fields = [field for field in db[table] if field.readable]
                    count = dbset.count()
                    try:
                        offset = int(vars.get('offset',None) or 0)
                        limits = (offset,int(vars.get('limit',None) or 1000)+offset)
                    except ValueError:
                        Row({'status':400,'error':'invalid limits','response':None})
                    if count > limits[1]-limits[0]:
                        Row({'status':400,'error':'too many records','response':None})
                    try:
                        response = dbset.select(limitby=limits,orderby=orderby,*fields)
                    except ValueError:
                        return Row({'status':400,'pattern':pattern,
                                    'error':'invalid path','response':None})
                    return Row({'status':200,'response':response,
                                'pattern':pattern,'count':count})
        return Row({'status':400,'error':'no matching pattern','response':None})


    def define_table(
        self,
        tablename,
        *fields,
        **args
        ):

        for key in args:
            if key not in [
                    'migrate',
                    'primarykey',
                    'fake_migrate',
                    'format',
                    'singular',
                    'plural',
                    'trigger_name',
                    'sequence_name',
                    'common_filter',
                    'polymodel',
                    'table_class']:
                raise SyntaxError, 'invalid table "%s" attribute: %s' \
                    % (tablename, key)
        if not isinstance(tablename,str):
            raise SyntaxError, "missing table name"
        tablename = cleanup(tablename)
        migrate = self._migrate_enabled and args.get('migrate',
                                                     self._migrate)
        fake_migrate = self._fake_migrate_all or args.get('fake_migrate',
                                                          self._fake_migrate)
        table_class = args.get('table_class',Table)
        format = args.get('format',None)
        trigger_name = args.get('trigger_name', None)
        sequence_name = args.get('sequence_name', None)
        primarykey =args.get('primarykey',None)
        polymodel = args.get('polymodel',None)
        singular = args.get('singular',tablename.replace('_',' ').capitalize())
        plural = args.get('plural',pluralize(singular.lower()).capitalize())
        lowertablename = tablename.lower()

        if tablename.startswith('_') or hasattr(self,lowertablename) or \
                regex_python_keywords.match(tablename):
            raise SyntaxError, 'invalid table name: %s' % tablename
        elif lowertablename in self.tables:
            raise SyntaxError, 'table already defined: %s' % tablename
        elif self.check_reserved:
            self.check_reserved_keyword(tablename)

        if self._common_fields:
            fields = [f for f in fields] + [f for f in self._common_fields]

        common_filter = args.get('common_filter', None)

        t = self[tablename] = table_class(self, tablename, *fields,
                                          **dict(primarykey=primarykey,
                                                 trigger_name=trigger_name,
                                                 sequence_name=sequence_name,
                                                 common_filter=common_filter))

        # db magic
        if self._uri in (None,'None'):
            return t

        t._create_references()

        if migrate or self._adapter.dbengine=='google:datastore':
            try:
                sql_locker.acquire()
                self._adapter.create_table(t,migrate=migrate,
                                           fake_migrate=fake_migrate,
                                           polymodel=polymodel)
            finally:
                sql_locker.release()
        else:
            t._dbt = None
        self.tables.append(tablename)
        t._format = format
        t._singular = singular
        t._plural = plural
        t._actual = True
        return t

    def __iter__(self):
        for tablename in self.tables:
            yield self[tablename]

    def __getitem__(self, key):
        return dict.__getitem__(self, str(key))

    def __setitem__(self, key, value):
        dict.__setitem__(self, str(key), value)

    def __getattr__(self, key):
        return self[key]

    def __setattr__(self, key, value):
        if key[:1]!='_' and key in self:
            raise SyntaxError, \
                'Object %s exists and cannot be redefined' % key
        self[key] = value

    def __repr__(self):
        return '<DAL ' + dict.__repr__(self) + '>'

    def smart_query(self,fields,text):
        return Set(self, smart_query(fields,text))

    def __call__(self, query=None, ignore_common_filters=None):
        if isinstance(query,Table):
            query = query._id>0
        elif isinstance(query,Field):
            query = query!=None
        return Set(self, query, ignore_common_filters=ignore_common_filters)

    def commit(self):
        self._adapter.commit()

    def rollback(self):
        self._adapter.rollback()

    def close(self):
        if self._adapter in thread.instances:
            thread.instances.remove(self._adapter)
        self._adapter.close()

    def executesql(self, query, placeholders=None, as_dict=False):
        """
        placeholders is optional and will always be None when using DAL.
        If using raw SQL with placeholders, placeholders may be
        a sequence of values to be substituted in
        or, (if supported by the DB driver), a dictionary with keys
        matching named placeholders in your SQL.

        Added 2009-12-05 "as_dict" optional argument. Will always be
        None when using DAL. If using raw SQL can be set to True
        and the results cursor returned by the DB driver will be
        converted to a sequence of dictionaries keyed with the db
        field names. Tested with SQLite but should work with any database
        since the cursor.description used to get field names is part of the
        Python dbi 2.0 specs. Results returned with as_dict=True are
        the same as those returned when applying .to_list() to a DAL query.

        [{field1: value1, field2: value2}, {field1: value1b, field2: value2b}]

        --bmeredyk
        """
        if placeholders:
            self._adapter.execute(query, placeholders)
        else:
            self._adapter.execute(query)
        if as_dict:
            if not hasattr(self._adapter.cursor,'description'):
                raise RuntimeError, "database does not support executesql(...,as_dict=True)"
            # Non-DAL legacy db query, converts cursor results to dict.
            # sequence of 7-item sequences. each sequence tells about a column.
            # first item is always the field name according to Python Database API specs
            columns = self._adapter.cursor.description
            # reduce the column info down to just the field names
            fields = [f[0] for f in columns]
            # will hold our finished resultset in a list
            data = self._adapter.cursor.fetchall()
            # convert the list for each row into a dictionary so it's
            # easier to work with. row['field_name'] rather than row[0]
            return [dict(zip(fields,row)) for row in data]
        # see if any results returned from database
        try:
            return self._adapter.cursor.fetchall()
        except:
            return None

    def _update_referenced_by(self, other):
        for tablename in self.tables:
            by = self[tablename]._referenced_by
            by[:] = [item for item in by if not item[0] == other]

    def export_to_csv_file(self, ofile, *args, **kwargs):
        step = int(kwargs.get('max_fetch_rows,',500))
        write_colnames = kwargs['write_colnames'] = \
            kwargs.get("write_colnames", True)
        for table in self.tables:
            ofile.write('TABLE %s\r\n' % table)
            query = self[table]._id > 0
            nrows = self(query).count()
            kwargs['write_colnames'] = write_colnames
            for k in range(0,nrows,step):
                self(query).select(limitby=(k,k+step)).export_to_csv_file(
                    ofile, *args, **kwargs)
                kwargs['write_colnames'] = False
            ofile.write('\r\n\r\n')
        ofile.write('END')

    def import_from_csv_file(self, ifile, id_map=None, null='<NULL>',
                             unique='uuid', *args, **kwargs):
        #if id_map is None: id_map={}
        id_offset = {} # only used if id_map is None
        for line in ifile:
            line = line.strip()
            if not line:
                continue
            elif line == 'END':
                return
            elif not line.startswith('TABLE ') or not line[6:] in self.tables:
                raise SyntaxError, 'invalid file format'
            else:
                tablename = line[6:]
                self[tablename].import_from_csv_file(
                    ifile, id_map, null, unique, id_offset, *args, **kwargs)

class SQLALL(object):
    """
    Helper class providing a comma-separated string having all the field names
    (prefixed by table name and '.')

    normally only called from within gluon.sql
    """

    def __init__(self, table):
        self._table = table

    def __str__(self):
        return ', '.join([str(field) for field in self._table])


class Reference(int):

    def __allocate(self):
        if not self._record:
            self._record = self._table[int(self)]
        if not self._record:
            raise RuntimeError, "Using a recursive select but encountered a broken reference: %s %d"%(self._table, int(self))

    def __getattr__(self, key):
        if key == 'id':
            return int(self)
        self.__allocate()
        return self._record.get(key, None)

    def get(self, key):
        return self.__getattr__(key)

    def __setattr__(self, key, value):
        if key.startswith('_'):
            int.__setattr__(self, key, value)
            return
        self.__allocate()
        self._record[key] =  value

    def __getitem__(self, key):
        if key == 'id':
            return int(self)
        self.__allocate()
        return self._record.get(key, None)

    def __setitem__(self,key,value):
        self.__allocate()
        self._record[key] = value


def Reference_unpickler(data):
    return marshal.loads(data)

def Reference_pickler(data):
    try:
        marshal_dump = marshal.dumps(int(data))
    except AttributeError:
        marshal_dump = 'i%s' % struct.pack('<i', int(data))
    return (Reference_unpickler, (marshal_dump,))

copy_reg.pickle(Reference, Reference_pickler, Reference_unpickler)


class Table(dict):

    """
    an instance of this class represents a database table

    Example::

        db = DAL(...)
        db.define_table('users', Field('name'))
        db.users.insert(name='me') # print db.users._insert(...) to see SQL
        db.users.drop()
    """

    def __init__(
        self,
        db,
        tablename,
        *fields,
        **args
        ):
        """
        Initializes the table and performs checking on the provided fields.

        Each table will have automatically an 'id'.

        If a field is of type Table, the fields (excluding 'id') from that table
        will be used instead.

        :raises SyntaxError: when a supplied field is of incorrect type.
        """

        self._actual = False # set to True by define_table()
        self._tablename = tablename
        self._sequence_name = args.get('sequence_name',None) or \
            db and db._adapter.sequence_name(tablename)
        self._trigger_name = args.get('trigger_name',None) or \
            db and db._adapter.trigger_name(tablename)
        self._common_filter = args.get('common_filter', None)

        self._before_insert = []
        self._before_update = [lambda self,fs:self.delete_uploaded_files(fs)]
        self._before_delete = [lambda self:self.delete_uploaded_files()]
        self._after_insert = []
        self._after_update = []
        self._after_delete = []

        primarykey = args.get('primarykey', None)
        fieldnames,newfields=set(),[]
        if primarykey:
            if not isinstance(primarykey,list):
                raise SyntaxError, \
                    "primarykey must be a list of fields from table '%s'" \
                    % tablename
            self._primarykey = primarykey
        elif not [f for f in fields if isinstance(f,Field) and f.type=='id']:
            field = Field('id', 'id')
            newfields.append(field)
            fieldnames.add('id')
            self._id = field
        for field in fields:
            if not isinstance(field, (Field, Table)):
                raise SyntaxError, \
                    'define_table argument is not a Field or Table: %s' % field
            elif isinstance(field, Field) and not field.name in fieldnames:
                if hasattr(field, '_db'):
                    field = copy.copy(field)
                newfields.append(field)
                fieldnames.add(field.name)
                if field.type=='id':
                    self._id = field
            elif isinstance(field, Table):
                table = field
                for field in table:
                    if not field.name in fieldnames and not field.type=='id':
                        t2 = not table._actual and self._tablename
                        field = field.clone(point_self_references_to=t2)
                        newfields.append(field)
                        fieldnames.add(field.name)
            else:
                # let's ignore new fields with duplicated names!!!
                pass
        fields = newfields
        self._db = db
        tablename = tablename
        self._fields = SQLCallableList()
        self.virtualfields = []
        fields = list(fields)

        if db and self._db._adapter.uploads_in_blob==True:
            for field in fields:
                if isinstance(field, Field) and field.type == 'upload'\
                        and field.uploadfield is True:
                    tmp = field.uploadfield = '%s_blob' % field.name
        if isinstance(field.uploadfield,str) and \
                not [f for f in fields if f.name==field.uploadfield]:
            fields.append(self._db.Field(field.uploadfield,'blob',default=''))

        lower_fieldnames = set()
        reserved = dir(Table) + ['fields']
        for field in fields:
            if db and db.check_reserved:
                db.check_reserved_keyword(field.name)
            elif field.name in reserved:
                raise SyntaxError, "field name %s not allowed" % field.name

            if field.name.lower() in lower_fieldnames:
                raise SyntaxError, "duplicate field %s in table %s" \
                    % (field.name, tablename)
            else:
                lower_fieldnames.add(field.name.lower())

            self.fields.append(field.name)
            self[field.name] = field
            if field.type == 'id':
                self['id'] = field
            field.tablename = field._tablename = tablename
            field.table = field._table = self
            field.db = field._db = self._db
            if self._db and not field.type in ('text','blob') and \
                    self._db._adapter.maxcharlength < field.length:
                field.length = self._db._adapter.maxcharlength
            if field.requires is DEFAULT:
                field.requires = sqlhtml_validators(field)
        self.ALL = SQLALL(self)

        if hasattr(self,'_primarykey'):
            for k in self._primarykey:
                if k not in self.fields:
                    raise SyntaxError, \
                        "primarykey must be a list of fields from table '%s " % tablename
                else:
                    self[k].notnull = True

    @property
    def fields(self):
        return self._fields

    def update(self,*args,**kwargs):
        raise RuntimeError, "Syntax Not Supported"

    def _enable_record_versioning(self,
                                  archive_db=None,
                                  archive_name = '%(tablename)s_archive',
                                  current_record = 'current_record',
                                  is_active = 'is_active'):
        archive_db = archive_db or self._db
        fieldnames = self.fields()
        archive_name = archive_name % dict(tablename=self._tablename)
        field_type = self if archive_db is self._db else 'bigint'
        archive_table = archive_db.define_table(
            archive_name,
            Field(current_record,field_type),
            *[field.clone(unique=False) for field in self])
        self._before_update.append(
            lambda qset,fs,at=archive_table,cn=current_record:
                archive_record(qset,fs,at,cn))
        if is_active and is_active in fieldnames:
            self._before_delete.append(
                lambda qset: qset.update(is_active=False))
            newquery = lambda query, t=self: t.is_active == True
            query = self._common_filter
            if query:
                newquery = query & newquery
            self._common_filter = newquery

    def _validate(self,**vars):
        errors = Row()
        for key,value in vars.items():
            value,error = self[key].validate(value)
            if error:
                errors[key] = error
        return errors

    def _create_references(self):
        pr = self._db._pending_references
        self._referenced_by = []
        for fieldname in self.fields:
            field=self[fieldname]
            if isinstance(field.type,str) and field.type[:10] == 'reference ':
                ref = field.type[10:].strip()
                if not ref.split():
                    raise SyntaxError, 'Table: reference to nothing: %s' %ref
                refs = ref.split('.')
                rtablename = refs[0]
                if not rtablename in self._db:
                    pr[rtablename] = pr.get(rtablename,[]) + [field]
                    continue
                rtable = self._db[rtablename]
                if len(refs)==2:
                    rfieldname = refs[1]
                    if not hasattr(rtable,'_primarykey'):
                        raise SyntaxError,\
                            'keyed tables can only reference other keyed tables (for now)'
                    if rfieldname not in rtable.fields:
                        raise SyntaxError,\
                            "invalid field '%s' for referenced table '%s' in table '%s'" \
                            % (rfieldname, rtablename, self._tablename)
                rtable._referenced_by.append((self._tablename, field.name))
        for referee in pr.get(self._tablename,[]):
            self._referenced_by.append((referee._tablename,referee.name))

    def _filter_fields(self, record, id=False):
        return dict([(k, v) for (k, v) in record.items() if k
                     in self.fields and (self[k].type!='id' or id)])

    def _build_query(self,key):
        """ for keyed table only """
        query = None
        for k,v in key.iteritems():
            if k in self._primarykey:
                if query:
                    query = query & (self[k] == v)
                else:
                    query = (self[k] == v)
            else:
                raise SyntaxError, \
                'Field %s is not part of the primary key of %s' % \
                (k,self._tablename)
        return query

    def __getitem__(self, key):
        if not key:
            return None
        elif isinstance(key, dict):
            """ for keyed table """
            query = self._build_query(key)
            rows = self._db(query).select()
            if rows:
                return rows[0]
            return None
        elif str(key).isdigit() or 'google' in drivers and isinstance(key, Key):
            return self._db(self._id == key).select(limitby=(0,1)).first()
        elif key:
            return dict.__getitem__(self, str(key))

    def __call__(self, key=DEFAULT, **kwargs):
        for_update = kwargs.get('_for_update',False)
        if '_for_update' in kwargs: del kwargs['_for_update']
        if not key is DEFAULT:
            if isinstance(key, Query):
                record = self._db(key).select(
                    limitby=(0,1),for_update=for_update).first()
            elif not str(key).isdigit():
                record = None
            else:
                record = self._db(self._id == key).select(
                    limitby=(0,1),for_update=for_update).first()
            if record:
                for k,v in kwargs.items():
                    if record[k]!=v: return None
            return record
        elif kwargs:
            query = reduce(lambda a,b:a&b,[self[k]==v for k,v in kwargs.items()])
            return self._db(query).select(limitby=(0,1),for_update=for_update).first()
        else:
            return None

    def __setitem__(self, key, value):
        if isinstance(key, dict) and isinstance(value, dict):
            """ option for keyed table """
            if set(key.keys()) == set(self._primarykey):
                value = self._filter_fields(value)
                kv = {}
                kv.update(value)
                kv.update(key)
                if not self.insert(**kv):
                    query = self._build_query(key)
                    self._db(query).update(**self._filter_fields(value))
            else:
                raise SyntaxError,\
                    'key must have all fields from primary key: %s'%\
                    (self._primarykey)
        elif str(key).isdigit():
            if key == 0:
                self.insert(**self._filter_fields(value))
            elif self._db(self._id == key)\
                    .update(**self._filter_fields(value)) is None:
                raise SyntaxError, 'No such record: %s' % key
        else:
            if isinstance(key, dict):
                raise SyntaxError,\
                    'value must be a dictionary: %s' % value
            dict.__setitem__(self, str(key), value)

    def __delitem__(self, key):
        if isinstance(key, dict):
            query = self._build_query(key)
            if not self._db(query).delete():
                raise SyntaxError, 'No such record: %s' % key
        elif not str(key).isdigit() or not self._db(self._id == key).delete():
            raise SyntaxError, 'No such record: %s' % key

    def __getattr__(self, key):
        return self[key]

    def __setattr__(self, key, value):
        if key[:1]!='_' and key in self:
            raise SyntaxError, 'Object exists and cannot be redefined: %s' % key
        self[key] = value

    def __iter__(self):
        for fieldname in self.fields:
            yield self[fieldname]

    def __repr__(self):
        return '<Table ' + dict.__repr__(self) + '>'

    def __str__(self):
        if self.get('_ot', None):
            if 'Oracle' in str(type(self._db._adapter)):     # <<< patch
                return '%s %s' % (self._ot, self._tablename) # <<< patch
            return '%s AS %s' % (self._ot, self._tablename)
        return self._tablename

    def _drop(self, mode = ''):
        return self._db._adapter._drop(self, mode)

    def drop(self, mode = ''):
        return self._db._adapter.drop(self,mode)

    def _listify(self,fields,update=False):
        new_fields = []
        new_fields_names = []
        for name in fields:
            if not name in self.fields:
                if name != 'id':
                    raise SyntaxError, 'Field %s does not belong to the table' % name
            else:
                field = self[name]
                value = fields[name]
                if field.filter_in: value = field.filter_in(value)
                new_fields.append((field,value))
                new_fields_names.append(name)
        for ofield in self:
            if not ofield.name in new_fields_names:
                if not update and not ofield.default is None:
                    new_fields.append((ofield,ofield.default))
                elif update and not ofield.update is None:
                    new_fields.append((ofield,ofield.update))
        for ofield in self:
            if ofield.compute:
                new_fields.append((ofield,ofield.compute(Row(fields))))
            if not update and ofield.required and not ofield.name in new_fields_names:
                raise SyntaxError,'Table: missing required field: %s' % ofield.name
        return new_fields

    def _attempt_upload(self, fields):
        for field in self:
            if field.type=='upload' and field.name in fields:
                value = fields[field.name]
                if value and not isinstance(value,str):
                    if hasattr(value,'file') and hasattr(value,'filename'):
                        new_name = field.store(value.file,filename=value.filename)
                    elif hasattr(value,'read') and hasattr(value,'name'):
                        new_name = field.store(value,filename=value.name)
                    else:
                        raise RuntimeError, "Unable to handle upload"
                    fields[field.name] = new_name

    def _insert(self, **fields):
        return self._db._adapter._insert(self,self._listify(fields))

    def insert(self, **fields):
        self._attempt_upload(fields)
        if any(f(fields) for f in self._before_insert): return 0
        ret =  self._db._adapter.insert(self,self._listify(fields))
        if ret and self._after_insert:
            fields = Row(fields)
            [f(fields,ret) for f in self._after_insert]
        return ret

    def validate_and_insert(self,**fields):
        response = Row()
        response.errors = Row()
        new_fields = copy.copy(fields)
        for key,value in fields.items():
            value,error = self[key].validate(value)
            if error:
                response.errors[key] = error
            else:
                new_fields[key] = value
        if not response.errors:
            response.id = self.insert(**new_fields)
        else:
            response.id = None
        return response

    def update_or_insert(self, _key=DEFAULT, **values):
        if _key is DEFAULT:
            record = self(**values)
        else:
            record = self(_key)
        if record:
            record.update_record(**values)
            newid = None
        else:
            newid = self.insert(**values)
        return newid

    def bulk_insert(self, items):
        """
        here items is a list of dictionaries
        """
        items = [self._listify(item) for item in items]
        if any(f(item) for item in items for f in self._before_insert):return 0
        ret = self._db._adapter.bulk_insert(self,items)
        ret and [[f(item,ret[k]) for k,item in enumerate(items)] for f in self._after_insert]
        return ret

    def _truncate(self, mode = None):
        return self._db._adapter._truncate(self, mode)

    def truncate(self, mode = None):
        return self._db._adapter.truncate(self, mode)

    def import_from_csv_file(
        self,
        csvfile,
        id_map=None,
        null='<NULL>',
        unique='uuid',
        id_offset={}, # id_offset only used when id_map is None
        *args, **kwargs
        ):
        """
        import records from csv file. Column headers must have same names as
        table fields. field 'id' is ignored. If column names read 'table.file'
        the 'table.' prefix is ignored.
        'unique' argument is a field which must be unique
        (typically a uuid field)
        'restore' argument is default False.
        If set True will remove old values
        in table first.
        'id_map' If set to None will not map id.
        The import will keep the id numbers in the restored table. 
        This assumes that there is an field of type id that
        is integer and in incrementing order. 
        Will keep the id numbers in restored table.
      """

        delimiter = kwargs.get('delimiter', ',')
        quotechar = kwargs.get('quotechar', '"')
        quoting = kwargs.get('quoting', csv.QUOTE_MINIMAL)
        restore = kwargs.get('restore', False)
        if restore:
            self._db[self].truncate()

        reader = csv.reader(csvfile, delimiter=delimiter,
                            quotechar=quotechar, quoting=quoting)
        colnames = None
        if isinstance(id_map, dict):
            if not self._tablename in id_map:
                id_map[self._tablename] = {}
            id_map_self = id_map[self._tablename]

        def fix(field, value, id_map, id_offset):
            list_reference_s='list:reference'
            if value == null:
                value = None
            elif field.type=='blob':
                value = base64.b64decode(value)
            elif field.type=='double' or field.type=='float':
                if not value.strip():
                    value = None
                else:
                    value = float(value)
            elif field.type in ('integer','bigint'):
                if not value.strip():
                    value = None
                else:
                    value = int(value)
            elif field.type.startswith('list:string'):
                value = bar_decode_string(value)
            elif field.type.startswith(list_reference_s):
                ref_table = field.type[len(list_reference_s):].strip()
                value = [id_map[ref_table][int(v)] \
                             for v in bar_decode_string(value)]
            elif field.type.startswith('list:'):
                value = bar_decode_integer(value)
            elif id_map and field.type.startswith('reference'):
                try:
                    value = id_map[field.type[9:].strip()][int(value)]
                except KeyError:
                    pass
            elif id_offset and field.type.startswith('reference'):
                try:
                    value = id_offset[field.type[9:].strip()]+int(value)
                except KeyError:
                    pass
            return (field.name, value)

        def is_id(colname):
            if colname in self:
                return self[colname].type == 'id'
            else:
                return False

        first = True
        for line in reader:
            if not line:
                break
            if not colnames:
                colnames = [x.split('.',1)[-1] for x in line][:len(line)]
                cols, cid = [], []
                for i,colname in enumerate(colnames):
                    if is_id(colname):
                        cid = i
                    else:
                        cols.append(i)
                    if colname == unique:
                        unique_idx = i
            else:
                items = [fix(self[colnames[i]], line[i], id_map, id_offset) \
                             for i in cols if colnames[i] in self.fields]
                if not id_map and cid:
                    csv_id = int(line[cid])
                    curr_id = self.insert(**dict(items))
                    del_id = curr_id
                    if first:
                        first = False
                        # First curr_id is bigger than csv_id, 
                        # then we are not restoring but
                        # extending db table with csv db table
                        if curr_id>csv_id:
                            id_offset[self._tablename] = curr_id-csv_id
                        else:
                            id_offset[self._tablename] = 0
                    # create new id until we get the same as old_id
                    while curr_id<csv_id+id_offset[self._tablename]:
                        curr_id = self.insert(**dict(items))
                    # remove ids that are not used
                    while del_id<csv_id:
                        query = self._db[self][colnames[cid]] == del_id
                        self._db(query).delete()
                        del_id += 1
                # Validation. Check for duplicate of 'unique' &,
                # if present, update instead of insert.
                elif not unique or unique not in colnames:
                    new_id = self.insert(**dict(items))
                else:
                    unique_value = line[unique_idx]
                    query = self._db[self][unique] == unique_value
                    record = self._db(query).select().first()
                    if record:
                        record.update_record(**dict(items))
                        new_id = record[self._id.name]
                    else:
                        new_id = self.insert(**dict(items))
                if id_map and cid != []:
                    id_map_self[int(line[cid])] = new_id

    def with_alias(self, alias):
        return self._db._adapter.alias(self,alias)

    def on(self, query):
        return Expression(self._db,self._db._adapter.ON,self,query)

def archive_record(qset,fs,archive_table,current_record):
    tablenames = qset.db._adapter.tables(qset.query)
    if len(tablenames)!=1: raise RuntimeError, "cannot update join"
    table = qset.db[tablenames[0]]
    for row in qset.select():
        fields = archive_table._filter_fields(row)
        fields[current_record] = row.id
        archive_table.insert(**fields)
    return False



class Expression(object):

    def __init__(
        self,
        db,
        op,
        first=None,
        second=None,
        type=None,
        ):

        self.db = db
        self.op = op
        self.first = first
        self.second = second
        ### self._tablename =  first._tablename ## CHECK
        if not type and first and hasattr(first,'type'):
            self.type = first.type
        else:
            self.type = type

    def sum(self):
        return Expression(self.db, self.db._adapter.AGGREGATE, self, 'SUM', self.type)

    def max(self):
        return Expression(self.db, self.db._adapter.AGGREGATE, self, 'MAX', self.type)

    def min(self):
        return Expression(self.db, self.db._adapter.AGGREGATE, self, 'MIN', self.type)

    def len(self):
        return Expression(self.db, self.db._adapter.AGGREGATE, self, 'LENGTH', 'integer')

    def avg(self):
        return Expression(self.db, self.db._adapter.AGGREGATE, self, 'AVG', self.type)

    def lower(self):
        return Expression(self.db, self.db._adapter.LOWER, self, None, self.type)

    def upper(self):
        return Expression(self.db, self.db._adapter.UPPER, self, None, self.type)

    def year(self):
        return Expression(self.db, self.db._adapter.EXTRACT, self, 'year', 'integer')

    def month(self):
        return Expression(self.db, self.db._adapter.EXTRACT, self, 'month', 'integer')

    def day(self):
        return Expression(self.db, self.db._adapter.EXTRACT, self, 'day', 'integer')

    def hour(self):
        return Expression(self.db, self.db._adapter.EXTRACT, self, 'hour', 'integer')

    def minutes(self):
        return Expression(self.db, self.db._adapter.EXTRACT, self, 'minute', 'integer')

    def coalesce(self,*others):
        return Expression(self.db, self.db._adapter.COALESCE, self, others, self.type)

    def coalesce_zero(self):
        return Expression(self.db, self.db._adapter.COALESCE_ZERO, self, None, self.type)

    def seconds(self):
        return Expression(self.db, self.db._adapter.EXTRACT, self, 'second', 'integer')

    def __getslice__(self, start, stop):
        if start < 0:
            pos0 = '(%s - %d)' % (self.len(), abs(start) - 1)
        else:
            pos0 = start + 1

        if stop < 0:
            length = '(%s - %d - %s)' % (self.len(), abs(stop) - 1, pos0)
        elif stop == sys.maxint:
            length = self.len()
        else:
            length = '(%s - %s)' % (stop + 1, pos0)
        return Expression(self.db,self.db._adapter.SUBSTRING,
                          self, (pos0, length), self.type)

    def __getitem__(self, i):
        return self[i:i + 1]

    def __str__(self):
        return self.db._adapter.expand(self,self.type)

    def __or__(self, other):  # for use in sortby
        return Expression(self.db,self.db._adapter.COMMA,self,other,self.type)

    def __invert__(self):
        if hasattr(self,'_op') and self.op == self.db._adapter.INVERT:
            return self.first
        return Expression(self.db,self.db._adapter.INVERT,self,type=self.type)

    def __add__(self, other):
        return Expression(self.db,self.db._adapter.ADD,self,other,self.type)

    def __sub__(self, other):
        if self.type in ('integer','bigint'):
            result_type = 'integer'
        elif self.type in ['date','time','datetime','double','float']:
            result_type = 'double'
        else:
            raise SyntaxError, "subtraction operation not supported for type"
        return Expression(self.db,self.db._adapter.SUB,self,other,
                          result_type)
    def __mul__(self, other):
        return Expression(self.db,self.db._adapter.MUL,self,other,self.type)

    def __div__(self, other):
        return Expression(self.db,self.db._adapter.DIV,self,other,self.type)

    def __mod__(self, other):
        return Expression(self.db,self.db._adapter.MOD,self,other,self.type)

    def __eq__(self, value):
        return Query(self.db, self.db._adapter.EQ, self, value)

    def __ne__(self, value):
        return Query(self.db, self.db._adapter.NE, self, value)

    def __lt__(self, value):
        return Query(self.db, self.db._adapter.LT, self, value)

    def __le__(self, value):
        return Query(self.db, self.db._adapter.LE, self, value)

    def __gt__(self, value):
        return Query(self.db, self.db._adapter.GT, self, value)

    def __ge__(self, value):
        return Query(self.db, self.db._adapter.GE, self, value)

    def like(self, value, case_sensitive=False):
        op = case_sensitive and self.db._adapter.LIKE or self.db._adapter.ILIKE
        return Query(self.db, op, self, value)

    def regexp(self, value):
        return Query(self.db, self.db._adapter.REGEXP, self, value)

    def belongs(self, *value):
        """
        Accepts the following inputs:
           field.belongs(1,2)
           field.belongs((1,2))
           field.belongs(query)

        Does NOT accept:
           field.belongs(1)
        """
        if len(value) == 1:
            value = value[0]
        if isinstance(value,Query):
            value = self.db(value)._select(value.first._table._id)
        return Query(self.db, self.db._adapter.BELONGS, self, value)

    def startswith(self, value):
        if not self.type in ('string', 'text'):
            raise SyntaxError, "startswith used with incompatible field type"
        return Query(self.db, self.db._adapter.STARTSWITH, self, value)

    def endswith(self, value):
        if not self.type in ('string', 'text'):
            raise SyntaxError, "endswith used with incompatible field type"
        return Query(self.db, self.db._adapter.ENDSWITH, self, value)

    def contains(self, value, all=False):
        if isinstance(value,(list, tuple)):
            subqueries = [self.contains(str(v).strip()) for v in value if str(v).strip()]
            return reduce(all and AND or OR, subqueries)
        if not self.type in ('string', 'text') and not self.type.startswith('list:'):
            raise SyntaxError, "contains used with incompatible field type"
        return Query(self.db, self.db._adapter.CONTAINS, self, value)

    def with_alias(self, alias):
        return Expression(self.db, self.db._adapter.AS, self, alias, self.type)

    # GIS functions

    def st_asgeojson(self, precision=15, options=0, version=1):
        return Expression(self.db, self.db._adapter.ST_ASGEOJSON, self,
            dict(precision=precision, options=options, version=version), 'dict')

    def st_astext(self):
        return Expression(self.db, self.db._adapter.ST_ASTEXT, self)

    def st_contained(self, value):
        return Query(self.db, self.db._adapter.ST_CONTAINS, value, self)

    def st_contains(self, value):
        return Query(self.db, self.db._adapter.ST_CONTAINS, self, value)

    def st_distance(self, other):
        return Expression(self.db,self.db._adapter.ST_DISTANCE,self,other,self.type)

    def st_equals(self, value):
        return Query(self.db, self.db._adapter.ST_EQUALS, self, value)

    def st_intersects(self, value):
        return Query(self.db, self.db._adapter.ST_INTERSECTS, self, value)

    def st_overlaps(self, value):
        return Query(self.db, self.db._adapter.ST_OVERLAPS, self, value)

    def st_simplify(self, value):
        return Expression(self.db, self.db._adapter.ST_SIMPLIFY, self, value)

    def st_touches(self, value):
        return Query(self.db, self.db._adapter.ST_TOUCHES, self, value)

    def st_within(self, value):
        return Query(self.db, self.db._adapter.ST_WITHIN, self, value)

    # for use in both Query and sortby


class SQLCustomType(object):
    """
    allows defining of custom SQL types

    Example::

        decimal = SQLCustomType(
            type ='double',
            native ='integer',
            encoder =(lambda x: int(float(x) * 100)),
            decoder = (lambda x: Decimal("0.00") + Decimal(str(float(x)/100)) )
            )

        db.define_table(
            'example',
            Field('value', type=decimal)
            )

    :param type: the web2py type (default = 'string')
    :param native: the backend type
    :param encoder: how to encode the value to store it in the backend
    :param decoder: how to decode the value retrieved from the backend
    :param validator: what validators to use ( default = None, will use the
        default validator for type)
    """

    def __init__(
        self,
        type='string',
        native=None,
        encoder=None,
        decoder=None,
        validator=None,
        _class=None,
        ):

        self.type = type
        self.native = native
        self.encoder = encoder or (lambda x: x)
        self.decoder = decoder or (lambda x: x)
        self.validator = validator
        self._class = _class or type

    def startswith(self, text=None):
        try:
            return self.type.startswith(self, text)
        except TypeError:
            return False

    def __getslice__(self, a=0, b=100):
        return None

    def __getitem__(self, i):
        return None

    def __str__(self):
        return self._class

class FieldVirtual(object):
    def __init__(self, f):
        self.f = f

class FieldLazy(object):
    def __init__(self, f, handler=None):
        self.f = f
        self.handler = handler


class Field(Expression):

    Virtual = FieldVirtual
    Lazy = FieldLazy

    """
    an instance of this class represents a database field

    example::

        a = Field(name, 'string', length=32, default=None, required=False,
            requires=IS_NOT_EMPTY(), ondelete='CASCADE',
            notnull=False, unique=False,
            uploadfield=True, widget=None, label=None, comment=None,
            uploadfield=True, # True means store on disk,
                              # 'a_field_name' means store in this field in db
                              # False means file content will be discarded.
            writable=True, readable=True, update=None, authorize=None,
            autodelete=False, represent=None, uploadfolder=None,
            uploadseparate=False # upload to separate directories by uuid_keys
                                 # first 2 character and tablename.fieldname
                                 # False - old behavior
                                 # True - put uploaded file in
                                 #   <uploaddir>/<tablename>.<fieldname>/uuid_key[:2]
                                 #        directory)
            uploadfs=None     # a pyfilesystem where to store upload

    to be used as argument of DAL.define_table

    allowed field types:
    string, boolean, integer, double, text, blob,
    date, time, datetime, upload, password

    strings must have a length of Adapter.maxcharlength by default (512 or 255 for mysql)
    fields should have a default or they will be required in SQLFORMs
    the requires argument is used to validate the field input in SQLFORMs

    """

    def __init__(
        self,
        fieldname,
        type='string',
        length=None,
        default=DEFAULT,
        required=False,
        requires=DEFAULT,
        ondelete='CASCADE',
        notnull=False,
        unique=False,
        uploadfield=True,
        widget=None,
        label=DEFAULT,
        comment=None,
        writable=True,
        readable=True,
        update=None,
        authorize=None,
        autodelete=False,
        represent=None,
        uploadfolder=None,
        uploadseparate=False,
        uploadfs=None,
        compute=None,
        custom_store=None,
        custom_retrieve=None,
        custom_retrieve_file_properties=None,
        custom_delete=None,
        filter_in = None,
        filter_out = None,
        custom_qualifier = None,
        ):
        self.db = None
        self.op = None
        self.first = None
        self.second = None
        if not isinstance(fieldname,str):
            raise SyntaxError, "missing field name"
        self.name = fieldname = cleanup(fieldname)
        if hasattr(Table,fieldname) or fieldname[0] == '_' or \
                regex_python_keywords.match(fieldname):
            raise SyntaxError, 'Field: invalid field name: %s' % fieldname
        if isinstance(type, Table):
            type = 'reference ' + type._tablename
        self.type = type  # 'string', 'integer'
        self.length = (length is None) and DEFAULTLENGTH.get(type,512) or length
        if default is DEFAULT:
            self.default = update or None
        else:
            self.default = default
        self.required = required  # is this field required
        self.ondelete = ondelete.upper()  # this is for reference fields only
        self.notnull = notnull
        self.unique = unique
        self.uploadfield = uploadfield
        self.uploadfolder = uploadfolder
        self.uploadseparate = uploadseparate
        self.uploadfs = uploadfs
        self.widget = widget
        if label is DEFAULT:
            self.label = fieldname.replace('_', ' ').title()
        else:
            self.label = label or ''
        self.comment = comment
        self.writable = writable
        self.readable = readable
        self.update = update
        self.authorize = authorize
        self.autodelete = autodelete
        if not represent and type in ('list:integer','list:string'):
            represent=lambda x,r=None: ', '.join(str(y) for y in x or [])
        self.represent = represent
        self.compute = compute
        self.isattachment = True
        self.custom_store = custom_store
        self.custom_retrieve = custom_retrieve
        self.custom_retrieve_file_properties = custom_retrieve_file_properties
        self.custom_delete = custom_delete
        self.filter_in = filter_in
        self.filter_out = filter_out
        self.custom_qualifier = custom_qualifier
        if self.label is None:
            self.label = fieldname.replace('_',' ').title()
        if requires is None:
            self.requires = []
        else:
            self.requires = requires

    def clone(self,point_self_references_to=False,**args):
        field = copy.copy(self)
        if point_self_references_to and \
                field.type == 'reference %s'+field._tablename:
            field.type = 'reference %s' % point_self_references_to
        field.__dict__.update(args)
        return field

    def store(self, file, filename=None, path=None):
        if self.custom_store:
            return self.custom_store(file,filename,path)
        if isinstance(file, cgi.FieldStorage):
            file = file.file
            filename = filename or file.filename
        elif not filename:
            filename = file.name
        filename = os.path.basename(filename.replace('/', os.sep)\
                                        .replace('\\', os.sep))
        m = re.compile('\.(?P<e>\w{1,5})$').search(filename)
        extension = m and m.group('e') or 'txt'
        uuid_key = web2py_uuid().replace('-', '')[-16:]
        encoded_filename = base64.b16encode(filename).lower()
        newfilename = '%s.%s.%s.%s' % \
            (self._tablename, self.name, uuid_key, encoded_filename)
        newfilename = newfilename[:(self.length - 1 - len(extension))] + '.' + extension
        if isinstance(self.uploadfield,Field):
            blob_uploadfield_name = self.uploadfield.uploadfield
            keys={self.uploadfield.name: newfilename,
                  blob_uploadfield_name: file.read()}
            self.uploadfield.table.insert(**keys)
        elif self.uploadfield == True:
            if path:
                pass
            elif self.uploadfolder:
                path = self.uploadfolder
            elif self.db._adapter.folder:
                path = os.path.join(self.db._adapter.folder, '..', 'uploads')
            else:
                raise RuntimeError,\
                    "you must specify a Field(...,uploadfolder=...)"
            if self.uploadseparate:
                if self.uploadfs:
                    raise RuntimeError, "not supported"
                path = os.path.join(path,"%s.%s" %(self._tablename, self.name),
                                    uuid_key[:2])
            if not os.path.exists(path):
                os.makedirs(path)
            pathfilename = os.path.join(path, newfilename)
            if self.uploadfs:
                dest_file = self.uploadfs.open(newfilename, 'wb')
            else:
                dest_file = open(pathfilename, 'wb')
            try:
                shutil.copyfileobj(file, dest_file)
            except IOError:
                raise IOError, 'Unable to store file "%s" because invalid permissions, readonly file system, or filename too long' % pathfilename
            dest_file.close()
        return newfilename

    def retrieve(self, name, path=None):
        if self.custom_retrieve:
            return self.custom_retrieve(name, path)
        import http
        if self.authorize or isinstance(self.uploadfield, str):
            row = self.db(self == name).select().first()
            if not row:
                raise http.HTTP(404)
        if self.authorize and not self.authorize(row):
            raise http.HTTP(403)
        m = regex_content.match(name)
        if not m or not self.isattachment:
            raise TypeError, 'Can\'t retrieve %s' % name
        file_properties = self.retrieve_file_properties(name,path)
        filename = file_properties['filename']
        if isinstance(self.uploadfield, str):  # ## if file is in DB
            stream = cStringIO.StringIO(row[self.uploadfield] or '')
        elif isinstance(self.uploadfield,Field):
            blob_uploadfield_name = self.uploadfield.uploadfield
            query = self.uploadfield == name
            data = self.uploadfield.table(query)[blob_uploadfield_name]
            stream = cStringIO.StringIO(data)
        elif self.uploadfs:
            # ## if file is on pyfilesystem
            stream = self.uploadfs.open(name, 'rb')
        else:
            # ## if file is on regular filesystem
            stream = open(os.path.join(file_properties['path'], name), 'rb')
        return (filename, stream)

    def retrieve_file_properties(self, name, path=None):
        if self.custom_retrieve_file_properties:
            return self.custom_retrieve_file_properties(name, path)
        try:
            m = regex_content.match(name)
            if not m or not self.isattachment:
                raise TypeError, 'Can\'t retrieve %s file properties' % name
            filename = base64.b16decode(m.group('name'), True)
            filename = regex_cleanup_fn.sub('_', filename)
        except (TypeError, AttributeError):
            filename = name
        if isinstance(self.uploadfield, str):  # ## if file is in DB
            return dict(path=None,filename=filename)
        elif isinstance(self.uploadfield,Field):
            return dict(path=None,filename=filename)
        else:
            # ## if file is on filesystem
            if path:
                pass
            elif self.uploadfolder:
                path = self.uploadfolder
            else:
                path = os.path.join(self.db._adapter.folder, '..', 'uploads')
            if self.uploadseparate:
                t = m.group('table')
                f = m.group('field')
                u = m.group('uuidkey')
                path = os.path.join(path,"%s.%s" % (t,f),u[:2])
            return dict(path=path,filename=filename)


    def formatter(self, value):
        if value is None or not self.requires:
            return value
        if not isinstance(self.requires, (list, tuple)):
            requires = [self.requires]
        elif isinstance(self.requires, tuple):
            requires = list(self.requires)
        else:
            requires = copy.copy(self.requires)
        requires.reverse()
        for item in requires:
            if hasattr(item, 'formatter'):
                value = item.formatter(value)
        return value

    def validate(self, value):
        if not self.requires:
            return (value, None)
        requires = self.requires
        if not isinstance(requires, (list, tuple)):
            requires = [requires]
        for validator in requires:
            (value, error) = validator(value)
            if error:
                return (value, error)
        return (value, None)

    def count(self, distinct=None):
        return Expression(self.db, self.db._adapter.COUNT, self, distinct, self.type)

    def __nonzero__(self):
        return True

    def __str__(self):
        try:
            return '%s.%s' % (self.tablename, self.name)
        except:
            return '<no table>.%s' % self.name


class Query(object):

    """
    a query object necessary to define a set.
    it can be stored or can be passed to DAL.__call__() to obtain a Set

    Example::

        query = db.users.name=='Max'
        set = db(query)
        records = set.select()

    """

    def __init__(
        self,
        db,
        op,
        first=None,
        second=None,
        ignore_common_filters = False,
        ):
        self.db = self._db = db
        self.op = op
        self.first = first
        self.second = second
        self.ignore_common_filters = ignore_common_filters

    def __str__(self):
        return self.db._adapter.expand(self)

    def __and__(self, other):
        return Query(self.db,self.db._adapter.AND,self,other)

    def __or__(self, other):
        return Query(self.db,self.db._adapter.OR,self,other)

    def __invert__(self):
        if self.op==self.db._adapter.NOT:
            return self.first
        return Query(self.db,self.db._adapter.NOT,self)


regex_quotes = re.compile("'[^']*'")


def xorify(orderby):
    if not orderby:
        return None
    orderby2 = orderby[0]
    for item in orderby[1:]:
        orderby2 = orderby2 | item
    return orderby2

def use_common_filters(query):
    return (query and hasattr(query,'ignore_common_filters') and \
                not query.ignore_common_filters)

class Set(object):

    """
    a Set represents a set of records in the database,
    the records are identified by the query=Query(...) object.
    normally the Set is generated by DAL.__call__(Query(...))

    given a set, for example
       set = db(db.users.name=='Max')
    you can:
       set.update(db.users.name='Massimo')
       set.delete() # all elements in the set
       set.select(orderby=db.users.id, groupby=db.users.name, limitby=(0,10))
    and take subsets:
       subset = set(db.users.id<5)
    """

    def __init__(self, db, query, ignore_common_filters = None):
        self.db = db
        self._db = db # for backward compatibility
        if not ignore_common_filters is None and \
                use_common_filters(query) == ignore_common_filters:
            query = copy.copy(query)
            query.ignore_common_filters = ignore_common_filters
        self.query = query

    def __call__(self, query, ignore_common_filters=False):
        if isinstance(query,Table):
            query = query._id>0
        elif isinstance(query,str):
            query = Expression(self.db,query)
        elif isinstance(query,Field):
            query = query!=None
        if self.query:
            return Set(self.db, self.query & query,
                       ignore_common_filters = ignore_common_filters)
        else:
            return Set(self.db, query,
                       ignore_common_filters = ignore_common_filters)

    def _count(self,distinct=None):
        return self.db._adapter._count(self.query,distinct)

    def _select(self, *fields, **attributes):
        adapter = self.db._adapter
        fields = adapter.expand_all(fields, adapter.tables(self.query))
        return adapter._select(self.query,fields,attributes)

    def _delete(self):
        tablename=self.db._adapter.get_table(self.query)
        return self.db._adapter._delete(tablename,self.query)

    def _update(self, **update_fields):
        tablename = self.db._adapter.get_table(self.query)
        fields = self.db[tablename]._listify(update_fields,update=True)
        return self.db._adapter._update(tablename,self.query,fields)

    def isempty(self):
        return not self.select(limitby=(0,1))

    def count(self,distinct=None):
        return self.db._adapter.count(self.query,distinct)

    def select(self, *fields, **attributes):
        if self.query is None:# and fields[0]._table._common_filter != None:
            return self(fields[0]._table).select(*fields,**attributes)
        adapter = self.db._adapter
        fields = adapter.expand_all(fields, adapter.tables(self.query))
        return adapter.select(self.query,fields,attributes)

    def nested_select(self,*fields,**attributes):
        return Expression(self.db,self._select(*fields,**attributes))

    def delete(self):
        tablename=self.db._adapter.get_table(self.query)
        table = self.db[tablename]
        if any(f(self) for f in table._before_delete): return 0
        ret = self.db._adapter.delete(tablename,self.query)
        ret and [f(self) for f in table._after_delete]
        return ret

    def update(self, **update_fields):
        tablename = self.db._adapter.get_table(self.query)
        table = self.db[tablename]
        table._attempt_upload(update_fields)
        if any(f(self,update_fields) for f in table._before_update): return 0
        fields = table._listify(update_fields,update=True)
        if not fields: raise SyntaxError, "No fields to update"
        ret = self.db._adapter.update(tablename,self.query,fields)
        ret and [f(self,update_fields) for f in table._after_update]
        return ret

    def update_naive(self, **update_fields):
        """
        same as update but does not call table._before_update and _after_update
        """
        tablename = self.db._adapter.get_table(self.query)
        table = self.db[tablename]
        fields = table._listify(update_fields,update=True)
        if not fields: raise SyntaxError, "No fields to update"
        ret = self.db._adapter.update(tablename,self.query,fields)
        return ret

    def validate_and_update(self, **update_fields):
        tablename = self.db._adapter.get_table(self.query)
        response = Row()
        response.errors = Row()
        new_fields = copy.copy(update_fields)
        for key,value in update_fields.items():
            value,error = self.db[tablename][key].validate(value)
            if error:
                response.errors[key] = error
            else:
                new_fields[key] = value
        table = self.db[tablename]
        if response.errors:
            response.updated = None
        else:
            if not any(f(self,new_fields) for f in table._before_update):
                fields = table._listify(new_fields,update=True)
                if not fields: raise SyntaxError, "No fields to update"
                ret = self.db._adapter.update(tablename,self.query,fields)
                ret and [f(self,new_fields) for f in table._after_update]
            else:
                ret = 0
            response.update = ret
        return response

    def delete_uploaded_files(self, upload_fields=None):
        table = self.db[self.db._adapter.tables(self.query)[0]]
        # ## mind uploadfield==True means file is not in DB
        if upload_fields:
            fields = upload_fields.keys()
        else:
            fields = table.fields
        fields = [f for f in fields if table[f].type == 'upload'
                   and table[f].uploadfield == True
                   and table[f].autodelete]
        if not fields:
            return False
        for record in self.select(*[table[f] for f in fields]):
            for fieldname in fields:
                field = table[fieldname]
                oldname = record.get(fieldname, None)
                if not oldname:
                    continue
                if upload_fields and oldname == upload_fields[fieldname]:
                    continue
                if field.custom_delete:
                    field.custom_delete(oldname)
                else:
                    uploadfolder = field.uploadfolder
                    if not uploadfolder:
                        uploadfolder = os.path.join(self.db._adapter.folder, '..', 'uploads')
                    if field.uploadseparate:
                        items = oldname.split('.')
                        uploadfolder = os.path.join(uploadfolder,
                                                    "%s.%s" % (items[0], items[1]),
                                                    items[2][:2])
                    oldpath = os.path.join(uploadfolder, oldname)
                    if os.path.exists(oldpath):
                        os.unlink(oldpath)
        return False

def update_record(pack, a=None):
    (colset, table, id) = pack
    b = a or dict(colset)
    c = dict([(k,v) for (k,v) in b.items() if k in table.fields and table[k].type!='id'])
    table._db(table._id==id,ignore_common_filters=True).update(**c)
    for (k, v) in c.items():
        colset[k] = v

class VirtualCommand(object):
    def __init__(self,method,row):
        self.method=method
        self.row=row
    def __call__(self,*args,**kwargs):
        return self.method(self.row,*args,**kwargs)

def lazy_virtualfield(f):
    f.__lazy__ = True
    return f

class Rows(object):

    """
    A wrapper for the return value of a select. It basically represents a table.
    It has an iterator and each row is represented as a dictionary.
    """

    # ## TODO: this class still needs some work to care for ID/OID

    def __init__(
        self,
        db=None,
        records=[],
        colnames=[],
        compact=True,
        rawrows=None
        ):
        self.db = db
        self.records = records
        self.colnames = colnames
        self.compact = compact
        self.response = rawrows

    def setvirtualfields(self,**keyed_virtualfields):
        """
        db.define_table('x',Field('number','integer'))
        if db(db.x).isempty(): [db.x.insert(number=i) for i in range(10)]

        from gluon.dal import lazy_virtualfield

        class MyVirtualFields(object):
            # normal virtual field (backward compatible, discouraged)
            def normal_shift(self): return self.x.number+1
            # lazy virtual field (because of @staticmethod)
            @lazy_virtualfield
            def lazy_shift(instance,row,delta=4): return row.x.number+delta
        db.x.virtualfields.append(MyVirtualFields())

        for row in db(db.x).select():
            print row.number, row.normal_shift, row.lazy_shift(delta=7)
        """
        if not keyed_virtualfields:
            return self
        for row in self.records:
            for (tablename,virtualfields) in keyed_virtualfields.items():
                attributes = dir(virtualfields)
                if not tablename in row:
                    box = row[tablename] = Row()
                else:
                    box = row[tablename]
                updated = False
                for attribute in attributes:
                    if attribute[0] != '_':
                        method = getattr(virtualfields,attribute)
                        if hasattr(method,'__lazy__'):
                            box[attribute]=VirtualCommand(method,row)
                        elif type(method)==types.MethodType:
                            if not updated:
                                virtualfields.__dict__.update(row)
                                updated = True
                            box[attribute]=method()
        return self

    def __and__(self,other):
        if self.colnames!=other.colnames: raise Exception, 'Cannot & incompatible Rows objects'
        records = self.records+other.records
        return Rows(self.db,records,self.colnames)

    def __or__(self,other):
        if self.colnames!=other.colnames: raise Exception, 'Cannot | incompatible Rows objects'
        records = self.records
        records += [record for record in other.records \
                        if not record in records]
        return Rows(self.db,records,self.colnames)

    def __nonzero__(self):
        if len(self.records):
            return 1
        return 0

    def __len__(self):
        return len(self.records)

    def __getslice__(self, a, b):
        return Rows(self.db,self.records[a:b],self.colnames)

    def __getitem__(self, i):
        row = self.records[i]
        keys = row.keys()
        if self.compact and len(keys) == 1 and keys[0] != '_extra':
            return row[row.keys()[0]]
        return row

    def __iter__(self):
        """
        iterator over records
        """

        for i in xrange(len(self)):
            yield self[i]

    def __str__(self):
        """
        serializes the table into a csv file
        """

        s = cStringIO.StringIO()
        self.export_to_csv_file(s)
        return s.getvalue()

    def first(self):
        if not self.records:
            return None
        return self[0]

    def last(self):
        if not self.records:
            return None
        return self[-1]

    def find(self,f):
        """
        returns a new Rows object, a subset of the original object,
        filtered by the function f
        """
        if not self.records:
            return Rows(self.db, [], self.colnames)
        records = []
        for i in range(0,len(self)):
            row = self[i]
            if f(row):
                records.append(self.records[i])
        return Rows(self.db, records, self.colnames)

    def exclude(self, f):
        """
        removes elements from the calling Rows object, filtered by the function f,
        and returns a new Rows object containing the removed elements
        """
        if not self.records:
            return Rows(self.db, [], self.colnames)
        removed = []
        i=0
        while i<len(self):
            row = self[i]
            if f(row):
                removed.append(self.records[i])
                del self.records[i]
            else:
                i += 1
        return Rows(self.db, removed, self.colnames)

    def sort(self, f, reverse=False):
        """
        returns a list of sorted elements (not sorted in place)
        """
        rows = Rows(self.db,[],self.colnames,compact=False)
        rows.records = sorted(self,key=f,reverse=reverse)
        return rows


    def group_by_value(self, field):
        """
        regroups the rows, by one of the fields
        """
        if not self.records:
            return {}
        key = str(field)
        grouped_row_group = dict()

        for row in self:
            value = row[key]
            if not value in grouped_row_group:
                grouped_row_group[value] = [row]
            else:
                grouped_row_group[value].append(row)
        return grouped_row_group

    def as_list(self,
                compact=True,
                storage_to_dict=True,
                datetime_to_str=True):
        """
        returns the data as a list or dictionary.
        :param storage_to_dict: when True returns a dict, otherwise a list(default True)
        :param datetime_to_str: convert datetime fields as strings (default True)
        """
        (oc, self.compact) = (self.compact, compact)
        if storage_to_dict:
            items = [item.as_dict(datetime_to_str) for item in self]
        else:
            items = [item for item in self]
        self.compact = compact
        return items


    def as_dict(self,
                key='id',
                compact=True,
                storage_to_dict=True,
                datetime_to_str=True):
        """
        returns the data as a dictionary of dictionaries (storage_to_dict=True) or records (False)

        :param key: the name of the field to be used as dict key, normally the id
        :param compact: ? (default True)
        :param storage_to_dict: when True returns a dict, otherwise a list(default True)
        :param datetime_to_str: convert datetime fields as strings (default True)
        """
        rows = self.as_list(compact, storage_to_dict, datetime_to_str)
        if isinstance(key,str) and key.count('.')==1:
            (table, field) = key.split('.')
            return dict([(r[table][field],r) for r in rows])
        elif isinstance(key,str):
            return dict([(r[key],r) for r in rows])
        else:
            return dict([(key(r),r) for r in rows])

    def export_to_csv_file(self, ofile, null='<NULL>', *args, **kwargs):
        """
        export data to csv, the first line contains the column names

        :param ofile: where the csv must be exported to
        :param null: how null values must be represented (default '<NULL>')
        :param delimiter: delimiter to separate values (default ',')
        :param quotechar: character to use to quote string values (default '"')
        :param quoting: quote system, use csv.QUOTE_*** (default csv.QUOTE_MINIMAL)
        :param represent: use the fields .represent value (default False)
        :param colnames: list of column names to use (default self.colnames)
                         This will only work when exporting rows objects!!!!
                         DO NOT use this with db.export_to_csv()
        """
        delimiter = kwargs.get('delimiter', ',')
        quotechar = kwargs.get('quotechar', '"')
        quoting = kwargs.get('quoting', csv.QUOTE_MINIMAL)
        represent = kwargs.get('represent', False)
        writer = csv.writer(ofile, delimiter=delimiter,
                            quotechar=quotechar, quoting=quoting)
        colnames = kwargs.get('colnames', self.colnames)
        write_colnames = kwargs.get('write_colnames',True)
        # a proper csv starting with the column names
        if write_colnames:
            writer.writerow(colnames)

        def none_exception(value):
            """
            returns a cleaned up value that can be used for csv export:
            - unicode text is encoded as such
            - None values are replaced with the given representation (default <NULL>)
            """
            if value is None:
                return null
            elif isinstance(value, unicode):
                return value.encode('utf8')
            elif isinstance(value,Reference):
                return int(value)
            elif hasattr(value, 'isoformat'):
                return value.isoformat()[:19].replace('T', ' ')
            elif isinstance(value, (list,tuple)): # for type='list:..'
                return bar_encode(value)
            return value

        for record in self:
            row = []
            for col in colnames:
                if not regex_table_field.match(col):
                    row.append(record._extra[col])
                else:
                    (t, f) = col.split('.')
                    field = self.db[t][f]
                    if isinstance(record.get(t, None), (Row,dict)):
                        value = record[t][f]
                    else:
                        value = record[f]
                    if field.type=='blob' and not value is None:
                        value = base64.b64encode(value)
                    elif represent and field.represent:
                        value = field.represent(value)
                    row.append(none_exception(value))
            writer.writerow(row)

    def xml(self):
        """
        serializes the table using sqlhtml.SQLTABLE (if present)
        """

        import sqlhtml
        return sqlhtml.SQLTABLE(self).xml()

    def json(self, mode='object', default=None):
        """
        serializes the table to a JSON list of objects
        """
        mode = mode.lower()
        if not mode in ['object', 'array']:
            raise SyntaxError, 'Invalid JSON serialization mode: %s' % mode

        def inner_loop(record, col):
            (t, f) = col.split('.')
            res = None
            if not regex_table_field.match(col):
                key = col
                res = record._extra[col]
            else:
                key = f
                if isinstance(record.get(t, None), Row):
                    res = record[t][f]
                else:
                    res = record[f]
            if mode == 'object':
                return (key, res)
            else:
                return res

        if mode == 'object':
            items = [dict([inner_loop(record, col) for col in
                     self.colnames]) for record in self]
        else:
            items = [[inner_loop(record, col) for col in self.colnames]
                     for record in self]
        if have_serializers:
            return serializers.json(items,default=default or serializers.custom_json)
        else:
            import simplejson
            return simplejson.dumps(items)

def Rows_unpickler(data):
    return cPickle.loads(data)

def Rows_pickler(data):
    return Rows_unpickler, \
        (cPickle.dumps(data.as_list(storage_to_dict=False,
                                    datetime_to_str=False)),)

copy_reg.pickle(Rows, Rows_pickler, Rows_unpickler)


################################################################################
# dummy function used to define some doctests
################################################################################

def test_all():
    """

    >>> if len(sys.argv)<2: db = DAL(\"sqlite://test.db\")
    >>> if len(sys.argv)>1: db = DAL(sys.argv[1])
    >>> tmp = db.define_table('users',\
              Field('stringf', 'string', length=32, required=True),\
              Field('booleanf', 'boolean', default=False),\
              Field('passwordf', 'password', notnull=True),\
              Field('uploadf', 'upload'),\
              Field('blobf', 'blob'),\
              Field('integerf', 'integer', unique=True),\
              Field('doublef', 'double', unique=True,notnull=True),\
              Field('datef', 'date', default=datetime.date.today()),\
              Field('timef', 'time'),\
              Field('datetimef', 'datetime'),\
              migrate='test_user.table')

   Insert a field

    >>> db.users.insert(stringf='a', booleanf=True, passwordf='p', blobf='0A',\
                       uploadf=None, integerf=5, doublef=3.14,\
                       datef=datetime.date(2001, 1, 1),\
                       timef=datetime.time(12, 30, 15),\
                       datetimef=datetime.datetime(2002, 2, 2, 12, 30, 15))
    1

    Drop the table

    >>> db.users.drop()

    Examples of insert, select, update, delete

    >>> tmp = db.define_table('person',\
              Field('name'),\
              Field('birth','date'),\
              migrate='test_person.table')
    >>> person_id = db.person.insert(name=\"Marco\",birth='2005-06-22')
    >>> person_id = db.person.insert(name=\"Massimo\",birth='1971-12-21')

    commented len(db().select(db.person.ALL))
    commented 2

    >>> me = db(db.person.id==person_id).select()[0] # test select
    >>> me.name
    'Massimo'
    >>> db(db.person.name=='Massimo').update(name='massimo') # test update
    1
    >>> db(db.person.name=='Marco').select().first().delete_record() # test delete
    1

    Update a single record

    >>> me.update_record(name=\"Max\")
    >>> me.name
    'Max'

    Examples of complex search conditions

    >>> len(db((db.person.name=='Max')&(db.person.birth<'2003-01-01')).select())
    1
    >>> len(db((db.person.name=='Max')&(db.person.birth<datetime.date(2003,01,01))).select())
    1
    >>> len(db((db.person.name=='Max')|(db.person.birth<'2003-01-01')).select())
    1
    >>> me = db(db.person.id==person_id).select(db.person.name)[0]
    >>> me.name
    'Max'

    Examples of search conditions using extract from date/datetime/time

    >>> len(db(db.person.birth.month()==12).select())
    1
    >>> len(db(db.person.birth.year()>1900).select())
    1

    Example of usage of NULL

    >>> len(db(db.person.birth==None).select()) ### test NULL
    0
    >>> len(db(db.person.birth!=None).select()) ### test NULL
    1

    Examples of search conditions using lower, upper, and like

    >>> len(db(db.person.name.upper()=='MAX').select())
    1
    >>> len(db(db.person.name.like('%ax')).select())
    1
    >>> len(db(db.person.name.upper().like('%AX')).select())
    1
    >>> len(db(~db.person.name.upper().like('%AX')).select())
    0

    orderby, groupby and limitby

    >>> people = db().select(db.person.name, orderby=db.person.name)
    >>> order = db.person.name|~db.person.birth
    >>> people = db().select(db.person.name, orderby=order)

    >>> people = db().select(db.person.name, orderby=db.person.name, groupby=db.person.name)

    >>> people = db().select(db.person.name, orderby=order, limitby=(0,100))

    Example of one 2 many relation

    >>> tmp = db.define_table('dog',\
               Field('name'),\
               Field('birth','date'),\
               Field('owner',db.person),\
               migrate='test_dog.table')
    >>> db.dog.insert(name='Snoopy', birth=None, owner=person_id)
    1

    A simple JOIN

    >>> len(db(db.dog.owner==db.person.id).select())
    1

    >>> len(db().select(db.person.ALL, db.dog.name,left=db.dog.on(db.dog.owner==db.person.id)))
    1

    Drop tables

    >>> db.dog.drop()
    >>> db.person.drop()

    Example of many 2 many relation and Set

    >>> tmp = db.define_table('author', Field('name'),\
                            migrate='test_author.table')
    >>> tmp = db.define_table('paper', Field('title'),\
                            migrate='test_paper.table')
    >>> tmp = db.define_table('authorship',\
            Field('author_id', db.author),\
            Field('paper_id', db.paper),\
            migrate='test_authorship.table')
    >>> aid = db.author.insert(name='Massimo')
    >>> pid = db.paper.insert(title='QCD')
    >>> tmp = db.authorship.insert(author_id=aid, paper_id=pid)

    Define a Set

    >>> authored_papers = db((db.author.id==db.authorship.author_id)&(db.paper.id==db.authorship.paper_id))
    >>> rows = authored_papers.select(db.author.name, db.paper.title)
    >>> for row in rows: print row.author.name, row.paper.title
    Massimo QCD

    Example of search condition using  belongs

    >>> set = (1, 2, 3)
    >>> rows = db(db.paper.id.belongs(set)).select(db.paper.ALL)
    >>> print rows[0].title
    QCD

    Example of search condition using nested select

    >>> nested_select = db()._select(db.authorship.paper_id)
    >>> rows = db(db.paper.id.belongs(nested_select)).select(db.paper.ALL)
    >>> print rows[0].title
    QCD

    Example of expressions

    >>> mynumber = db.define_table('mynumber', Field('x', 'integer'))
    >>> db(mynumber.id>0).delete()
    0
    >>> for i in range(10): tmp = mynumber.insert(x=i)
    >>> db(mynumber.id>0).select(mynumber.x.sum())[0](mynumber.x.sum())
    45

    >>> db(mynumber.x+2==5).select(mynumber.x + 2)[0](mynumber.x + 2)
    5

    Output in csv

    >>> print str(authored_papers.select(db.author.name, db.paper.title)).strip()
    author.name,paper.title\r
    Massimo,QCD

    Delete all leftover tables

    >>> DAL.distributed_transaction_commit(db)

    >>> db.mynumber.drop()
    >>> db.authorship.drop()
    >>> db.author.drop()
    >>> db.paper.drop()
    """
################################################################################
# deprecated since the new DAL; here only for backward compatibility
################################################################################

SQLField = Field
SQLTable = Table
SQLXorable = Expression
SQLQuery = Query
SQLSet = Set
SQLRows = Rows
SQLStorage = Row
SQLDB = DAL
GQLDB = DAL
DAL.Field = Field  # was necessary in gluon/globals.py session.connect
DAL.Table = Table  # was necessary in gluon/globals.py session.connect

################################################################################
# run tests
################################################################################

if __name__ == '__main__':
    import doctest
    doctest.testmod()



